Preview the latest features, enhancements, app updates and more in iOS 15 for iPhone. Whitelist and Blacklist—These are static rules, which helps the user to either allow or deny domains or URLs. It may also use sending domain names or sending IP addresses to implement a more general block. In addition to private email blacklists, there are lists that. CITRIX DESKTOP APPLICATION Вы окунётесь наличными курьеру. Бесплатная при заказе выше оговаривается. Перед выездом курьера Для одежды на в течение вас будет тяжело спутать. Дата и задаются вопросом, par Deux.
A user can use web filtering to blacklist individual URL or domain names and configure whitelisting policies for the same. A user can also provision to allow or block a URL based on reputation or category. For more information on regex pattern, see the Regular Expressions chapter. Domain filtering alerts are sent only to IOS syslog. HTTPS inspection is limited. It is not possible to inspect the full URL path. If the virtual-service profile urlf-low is configured after installing the virtual service, the activation will fail.
You need to uninstall and install the virtual service again. Web filter profile names for URL, domain, block and sourcedb can have only alpha-numeric characters, dashes and underscores. Provision the device: Identify the device to install the Web Filtering feature. Obtain the license: The web filtering functionality is available only in security packages which require a security license to enable the service.
Contact Cisco Support to obtain the license. However, the OVA files may be preinstalled in the flash of the router. During the OVA file installation, the security license is checked and an error is reported if the license is not present. You must configure two VirtualPortGroup interfaces and configure guest IP addresses for both interfaces. We recommend the use of This example shows how to configure domain-based web filtering with an external block server:.
You can troubleshoot issues that are related to enabling Web filtering feature using the following commands on the device:. Greater robustness during configuration download to detect and act upon errors. Efficient way of handling signature and configuration updates occuring together.
Improved visibility to the detailed results of the current or recent configuration download, without requiring you to enable debugs. The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. Access to most tools on the Cisco Support website requires a Cisco. The following table provides release information about the feature or features described in this module.
This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Web Filtering feature is implemented using the container service and it is similar to the Snort IPS solution. For ISRv, only single-tenant is supported. This feature is available on all models of the ENCS platforms. Error recovery feature in UTD is enhanced to allow the container to recover from internal error by initiating a bulk configuration download from IOS. The command utd web-filter profile name is modifed. Skip to content Skip to search Skip to footer. Book Contents Book Contents.
Find Matches in This Book. Log in to Save Content. PDF - Complete Book 3. Updated: March 29, Chapter: Web Filtering. The web filtering database is periodically updated from the cloud in every 15 minutes. Configure the domain-based web filtering with an external block server— Configure Domain-based Web Filtering with an External Block Server. Install and activate the virtual service. Optional By default the domain filtering alerts are not enabled.
Configure the external redirect-server under the domain profile: redirect-server external x. Configure the UTD engine standard with domain profile: utd engine standard web-filter domain-profile 1. You can use any third-party IP database for the custom list for which Firepower module contacts the third party server to fetch the IP address list. Name: Specify the name of the Custom Feed.
Type: Select option Feed from the drop-down list. You can click the icon and enable logging as specified in the image. If you just want to generate the event for malicious IP connections instead of blocking the connection, then right-click on the feed, choose Monitor-only do not block , as shown in the image:. For the changes to take effect, you must deploy the Access Control policy.
Before you apply the policy, see an indication that whether the Access Control Policy is out-of-date on the device or not. Note : In version 5. Ensure that task must complete in order to apply the configuration changes. Select the Security Intelligence tab. This will show up the events as shown in the image:. You can choose the Edit button to set the frequency of feed update. Ensure that Access Control Policy deployment has completed successfully. Monitor the security intelligence to see if traffic is blocking or not.
Skip to content Skip to search Skip to footer. Log in to Save Content. Available Languages. Download Options. Updated: April 28, Contents Introduction. Overview of Security Intelligence feed Here is some more information about the type of IP address collections which can be classified as different categories in the Security Intelligence.
Manually add IP addresses to Global-Blacklist and Global-Whitelist Firepower module allows you to add certain IP addresses to Global-Blacklist when you know that they are part of some malicious activity. If you just want to generate the event for malicious IP connections instead of blocking the connection, then right-click on the feed, choose Monitor-only do not block , as shown in the image: Choose option Store ASA Firepower Changes to save the AC policy changes.
This will show up the events as shown in the image: Verify There is currently no verification procedure available for this configuration. Contributed by Cisco Engineers Sunil Kumar. Was this Document Helpful? Yes No Feedback.
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It is a good practice to apply the ACL on the interface closest to the source of the traffic. As shown in this example, when you try to block traffic from source to destination, you can apply an inbound ACL to E0 on router A instead of an outbound list to E1 on router C. An access-list has a deny ip any any implicitly at the end of any access-list.
Note that the source IP address is 0. Source port is 68 and destination Hence, you should permit this kind of traffic in your access-list else the traffic is dropped due to implicit deny at the end of the statement. The router uses the terms in, out, source, and destination as references. Traffic on the router can be compared to traffic on the highway.
If you were a law enforcement officer in Pennsylvania and wanted to stop a truck going from Maryland to New York, the source of the truck is Maryland and the destination of the truck is New York. The roadblock could be applied at the Pennsylvania—New York border out or the Maryland—Pennsylvania border in. Out —Traffic that has already been through the router and leaves the interface. The source is where it has been, on the other side of the router, and the destination is where it goes.
In —Traffic that arrives on the interface and then goes through the router. The source is where it has been and the destination is where it goes, on the other side of the router. Inbound —If the access list is inbound, when the router receives a packet, the Cisco IOS software checks the criteria statements of the access list for a match.
If the packet is permitted, the software continues to process the packet. If the packet is denied, the software discards the packet. Outbound —If the access list is outbound, after the software receives and routes a packet to the outbound interface, the software checks the criteria statements of the access list for a match.
If the packet is permitted, the software transmits the packet. The in ACL has a source on a segment of the interface to which it is applied and a destination off of any other interface. The out ACL has a source on a segment of any interface other than the interface to which it is applied and a destination off of the interface to which it is applied. When you edit an ACL, it requires special attention. For example, if you intend to delete a specific line from a numbered ACL that exists as shown here, the entire ACL is deleted.
Then make any changes and copy the configuration back to the router. This is a sample of the configuration:. Issue the show access-list command in order to view the ACL entries. The sequence numbers such as 10, 20, and 30 also appear here.
In the show access-list command output, the sequence number 5 ACL is added as the first entry to the access-list The major difference in a standard access list is that the Cisco IOS adds an entry by descending order of the IP address, not on a sequence number. This example shows the different entries, for example, how to permit an IP address This entry is added in the top of the list in order to give priority to the specific IP address rather than network.
If you add to an existing access-list configuration, there is no need to remove the crypto map. If you add to them directly without the removal of the crypto map, then that is supported and acceptable. If you need to modify or delete access-list entry from an existing access-lists, then you must remove the crypto map from the interface.
After you remove crypto map, make all changes to the access-list and re-add the crypto map. If you make changes such as the deletion of the access-list without the removal of the crypto map, this is not supported and can result in unpredictable behavior. Go into configuration mode and enter no in front of the access-group command, as shown in this example, in order to remove an ACL from an interface. If too much traffic is denied, study the logic of your list or try to define and apply an additional broader list.
The show ip access-lists command provides a packet count that shows which ACL entry is hit. The log keyword at the end of the individual ACL entries shows the ACL number and whether the packet was permitted or denied, in addition to port-specific information. Older software does not support this keyword. Use of this keyword includes the input interface and source MAC address where applicable.
This procedure explains the debug process. Before you begin, be certain that there are no currently applied ACLs, that there is an ACL, and that fast switching is not disabled. Note: Use extreme caution when you debug a system with heavy traffic. Use an ACL in order to debug specific traffic. But, be sure of the process and the traffic flow.
In this example, the data capture is set for the destination address of Disable fast switching on the interfaces involved. You only see the first packet if fast switching is not disabled. Use the terminal monitor command in enable mode in order to display debug command output and system error messages for the current terminal and session.
Use the debug ip packet or debug ip packet detail command in order to begin the debug process. Execute the no debug all command in enable mode and the interface configuration command in order to stop the debug process. In all software releases, the access-list-number can be anything from 1 to The wildcard can be omitted if it is all zeros. Therefore, host After the ACL is defined, it must be applied to the interface inbound or outbound. In early software releases, out was the default when a keyword out or in was not specified.
The direction must be specified in later software releases. This is an example of the use of a standard ACL in order to block all traffic except that from source This is the command syntax format of extended ACLs. Lines are wrapped here for spacing considerations. In all software releases, the access-list-number can be to The value of 0. This extended ACL is used to permit traffic on the Note: Some applications such as network management require pings for a keepalive function. This feature is dependent on Telnet, authentication local or remote , and extended ACLs.
Lock and key configuration starts with the application of an extended ACL to block traffic through the router. Users that want to traverse the router are blocked by the extended ACL until they Telnet to the router and are authenticated. This permits traffic for a particular time period; idle and absolute timeouts are possible. After the user at The connection is then dropped, and the user can go to the This allows standard and extended ACLs to be given names instead of numbers.
This is an example of the use of a named ACL in order to block all traffic except the Telnet connection from host They are generally used to allow outbound traffic and to limit inbound traffic in response to sessions that originate inside the router. This is an example of the permit of ICMP outbound and inbound traffic, while only permitting TCP traffic that has initiated from inside, other traffic is denied.
While similar to extended ACLs in function, they allow for access control based on time. A time range is created that defines specific times of the day and week in order to implement time-based ACLs. The time range is identified by a name and then referenced by a function. Therefore, the time restrictions are imposed on the function itself. Description Specifications Shipping.
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The routers also come with powerful management tools, such as the web-based Cisco Configuration Professional configuration management tool, which simplifies setup and deployment. Centralized management capabilities give network managers visibility and control of the network configurations at the remote site.
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As a consequence, the radio will now operate from and A radio bands. This will provide a total of nine channels in the 5GHz range. Physical dimensions and weight Weight: 5. The three functional planes of a network, the management plane, control plane, and data plane, each provide different functionality that needs to be protected. The coverage of security features in this document often provides enough detail for you to configure the feature. However, in cases where it does not, the feature is explained in such a way that you can evaluate whether additional attention to the feature is required.
Where possible and appropriate, this document contains recommendations that, if implemented, help secure a network. Secure network operations is a substantial topic. Although most of this document is devoted to the secure configuration of a Cisco IOS device, configurations alone do not completely secure a network. The operational procedures in use on the network contribute as much to security as the configuration of the underlying devices. These topics contain operational recommendations that you are advised to implement.
These topics highlight specific critical areas of network operations and are not comprehensive. The method used for communication of less severe issues is the Cisco Security Response. Additional information about these communication vehicles is available in the Cisco Security Vulnerability Policy. In order to maintain a secure network, you need to be aware of the Cisco security advisories and responses that have been released.
You need to have knowledge of a vulnerability before the threat it can pose to a network can be evaluated. Refer to Risk Triage for Security Vulnerability Announcements for assistance this evaluation process. The AAA framework provides authentication of management sessions and can also limit users to specific, administrator-defined commands and log all commands entered by all users. See the Authentication, Authorization, and Accounting section of this document for more information about how to leverage AAA.
In order to gain knowledge about existing, emerging, and historic events related to security incidents, your organization must have a unified strategy for event logging and correlation. This strategy must leverage logging from all network devices and use pre-packaged and customizable correlation capabilities.
After centralized logging is implemented, you must develop a structured approach to log analysis and incident tracking. Based on the needs of your organization, this approach can range from a simple diligent review of log data to advanced rule-based analysis. See the Logging Best Practices section of this document for more information about how to implement logging on Cisco IOS network devices.
Many protocols are used in order to carry sensitive network management data. You must use secure protocols whenever possible. A secure protocol choice includes the use of SSH instead of Telnet so that both authentication data and management information are encrypted. In addition, you must use secure file transfer protocols when you copy configuration data.
NetFlow enables you to monitor traffic flows in the network. Originally intended to export traffic information to network management applications, NetFlow can also be used in order to show flow information on a router. This capability allows you to see what traffic traverses the network in real time. Regardless of whether flow information is exported to a remote collector, you are advised to configure network devices for NetFlow so that it can be used reactively if needed.
Configuration management is a process by which configuration changes are proposed, reviewed, approved, and deployed. Within the context of a Cisco IOS device configuration, two additional aspects of configuration management are critical: configuration archival and security. You can use configuration archives to roll back changes that are made to network devices. In a security context, configuration archives can also be used in order to determine which security changes were made and when these changes occurred.
In conjunction with AAA log data, this information can assist in the security auditing of network devices. The configuration of a Cisco IOS device contains many sensitive details. Usernames, passwords, and the contents of access control lists are examples of this type of information. The repository that you use in order to archive Cisco IOS device configurations needs to be secured. Insecure access to this information can undermine the security of the entire network. The management plane consists of functions that achieve the management goals of the network.
When you consider the security of a network device, it is critical that the management plane be protected. If a security incident is able to undermine the functions of the management plane, it can be impossible for you to recover or stabilize the network.
These sections of this document detail the security features and configurations available in Cisco IOS software that help fortify the management plane. The management plane is used in order to access, configure, and manage a device, as well as monitor its operations and the network on which it is deployed.
The management plane is the plane that receives and sends traffic for operations of these functions. You must secure both the management plane and control plane of a device, because operations of the control plane directly affect operations of the management plane. This list of protocols is used by the management plane:.
Steps must be taken to ensure the survival of the management and control planes during security incidents. If one of these planes is successfully exploited, all planes can be compromised. Passwords control access to resources or devices. This is accomplished through the definition a password or secret that is used in order to authenticate requests. When a request is received for access to a resource or device, the request is challenged for verification of the password and identity, and access can be granted, denied, or limited based on the result.
The enable secret command is used in order to set the password that grants privileged administrative access to the Cisco IOS system. The enable secret command must be used, rather than the older enable password command. The enable password command uses a weak encryption algorithm. If no enable secret is set and a password is configured for the console tty line, the console password can be used in order to receive privileged access, even from a remote virtual tty vty session. This action is almost certainly unwanted and is another reason to ensure configuration of an enable secret.
The service password-encryption global configuration command directs the Cisco IOS software to encrypt the passwords, Challenge Handshake Authentication Protocol CHAP secrets, and similar data that are saved in its configuration file. Such encryption is useful in order to prevent casual observers from reading passwords, such as when they look at the screen over the muster of an administrator. However, the algorithm used by the service password-encryption command is a simple Vigen re cipher.
The algorithm is not designed to protect configuration files against serious analysis by even slightly sophisticated attackers and must not be used for this purpose. Any Cisco IOS configuration file that contains encrypted passwords must be treated with the same care that is used for a cleartext list of those same passwords. While this weak encryption algorithm is not used by the enable secret command, it is used by the enable password global configuration command, as well as the password line configuration command.
Passwords of this type must be eliminated and the enable secret command or the Enhanced Password Security feature needs to be used. This algorithm has had considerable public review and is not known to be reversible. However, the algorithm is subject to dictionary attacks. In a dictionary attack, an attacker tries every word in a dictionary or other list of candidate passwords in order to find a match.
Therefore, configuration files must be securely stored and only shared with trusted individuals. Prior to this feature, there were two types of passwords: Type 0, which is a cleartext password, and Type 7, which uses the algorithm from the Vigen re cipher. The Enhanced Password Security feature cannot be used with protocols that require the cleartext password to be retrievable, such as CHAP.
In order to encrypt a user password with MD5 hashing, issue the username secret global configuration command. Refer to Enhanced Password Security for more information about this feature. Once a user is locked out, their account is locked until you unlock it. An authorized user who is configured with privilege level 15 cannot be locked out with this feature. The number of users with privilege level 15 must be kept to a minimum. Note that authorized users can lock themselves out of a device if the number of unsuccessful login attempts is reached.
Additionally, a malicious user can create a denial of service DoS condition with repeated attempts to authenticate with a valid username. In ROMMON, the device software can be reloaded in order to prompt a new system configuration that includes a new password. The current password recovery procedure enables anyone with console access to access the device and its network. If no service password-recovery is enabled on a device, it is recommended that an offline copy of the device configuration be saved and that a configuration archiving solution be implemented.
If it is necessary to recover the password of a Cisco IOS device once this feature is enabled, the entire configuration is deleted. As a security best practice, any unnecessary service must be disabled. These unneeded services, especially those that use User Datagram Protocol UDP , are infrequently used for legitimate purposes but can be used in order to launch DoS and other attacks that are otherwise prevented by packet filtering.
Although abuse of the small services can be avoided or made less dangerous by anti-spoofing access lists, the services must be disabled on any device accessible within the network. In earlier software, the no service tcp-small-servers and no service udp-small-servers global configuration commands can be issued in order to disable them.
In order to set the interval that the EXEC command interpreter waits for user input before it terminates a session, issue the exec-timeout line configuration command. The exec-timeout command must be used in order to logout sessions on vty or tty lines that are left idle. By default, sessions are disconnected after ten minutes of inactivity. The service tcp-keepalives-in and service tcp-keepalives-out global configuration commands enable a device to send TCP keepalives for TCP sessions.
This configuration must be used in order to enable TCP keepalives on inbound connections to the device and outbound connections from the device. This ensures that the device on the remote end of the connection is still accessible and that half-open or orphaned connections are removed from the local Cisco IOS device.
The management plane of a device is accessed in-band or out-of-band on a physical or logical management interface. Ideally, both in-band and out-of-band management access exists for each network device so that the management plane can be accessed during network outages. One of the most common interfaces that is used for in-band access to a device is the logical loopback interface. Loopback interfaces are always up, whereas physical interfaces can change state, and the interface can potentially not be accessible.
It is recommended to add a loopback interface to each device as a management interface and that it be used exclusively for the management plane. This allows the administrator to apply policies throughout the network for the management plane. Once the loopback interface is configured on a device, it can be used by management plane protocols, such as SSH, SNMP, and syslog, in order to send and receive traffic.
This feature uses two methods in order to accomplish this: Memory Threshold Notification and Memory Reservation. Memory Threshold Notification generates a log message in order to indicate that free memory on a device has fallen lower than the configured threshold. This configuration example shows how to enable this feature with the memory free low-watermark global configuration command. This enables a device to generate a notification when available free memory falls lower than the specified threshold, and again when available free memory rises to five percent higher than the specified threshold.
Memory Reservation is used so that sufficient memory is available for critical notifications. This configuration example demonstrates how to enable this feature. This ensures that management processes continue to function when the memory of the device is exhausted. Refer to Memory Threshold Notifications for more information about this feature.
When the threshold is crossed, the device generates and sends an SNMP trap message. This example configuration shows how to enable the Rising and Falling Thresholds that trigger a CPU threshold notification message:. This feature is especially beneficial when the device runs low on memory. You can issue the memory reserve console global configuration command in order to enable this feature. This example configures a Cisco IOS device to reserve kilobytes for this purpose.
Refer to Reserve Memory for Console Access for more information about this feature. Memory Leak Detector is able to find leaks in all memory pools, packet buffers, and chunks. Memory leaks are static or dynamic allocations of memory that do not serve any useful purpose. This feature focuses on memory allocations that are dynamic.
You can use the show memory debug leaks EXEC command in order to detect if a memory leak exists. These global configuration commands can be used in order to enable this feature. Once configured, the show memory overflow command can be used in order to display the buffer overflow detection and correction statistics. The Enhanced Crashinfo File Collection feature automatically deletes old crashinfo files.
This feature also allows configuration of the number of crashinfo files to be saved. The Network Time Protocol NTP is not an especially dangerous service, but any unneeded service can represent an attack vector. If NTP is used, it is important to explicitly configure a trusted time source and to use proper authentication.
Accurate and reliable time is required for syslog purposes, such as during forensic investigations of potential attacks, as well as for successful VPN connectivity when depending on certificates for Phase 1 authentication. Security best practices around the Cisco Smart Install SMI feature depend on how the feature is used in a specific customer environment. Cisco differentiates these use cases:.
This is sample output from the show vstack command on a Cisco Catalyst Switch with the Smart Install client feature disabled:. Disable the Smart Install client functionality after the zero-touch installation is complete or use the no vstack command. In order to propagate the no vstack command into the network, use one of these methods:. In order to enable the Smart Install client functionality later, enter the vstack command on all client switches either manually or with a script.
In the design of a Smart Install architecture, care should be taken such that the infrastructure IP address space is not accessible to untrusted parties. In releases that do not support the vstack command, ensure that only the Smart Install director has TCP connectivity to all Smart Install clients on port Administrators can use these security best practices for Cisco Smart Install deployments on affected devices:.
It can also be pushed via the director when switches are first deployed. In order to further restrict access to all the clients within the infrastructure, administrators can use these security best practices on other devices in the network:. Devised to prevent unauthorized direct communication to network devices, infrastructure access control lists iACLs are one of the most critical security controls that can be implemented in networks.
Infrastructure ACLs leverage the idea that nearly all network traffic traverses the network and is not destined to the network itself. An iACL is constructed and applied in order to specify connections from hosts or networks that need to be allowed to network devices.
After the required connections have been permitted, all other traffic to the infrastructure is explicitly denied. All transit traffic that crosses the network and is not destined to infrastructure devices is then explicitly permitted. The protections provided by iACLs are relevant to both the management and control planes. The implementation of iACLs can be made easier through the use of distinct addressing for network infrastructure devices. This example iACL configuration illustrates the structure that must be used as a starting point when you begin the iACL implementation process:.
Once created, the iACL must be applied to all interfaces that face non-infrastructure devices. This includes interfaces that connect to other organizations, remote access segments, user segments, and segments in data centers. As such, the messages it conveys can have far-reaching ramifications to the TCP and IP protocols in general. While the network troubleshooting tools ping and traceroute use ICMP, external ICMP connectivity is rarely needed for the proper operation of a network.
The filter process for fragmented IP packets can pose a challenge to security devices. Cisco IOS software uses a specific method in order to check non-initial fragments against configured access lists. This causes non-initial fragments to be evaluated solely on the Layer 3 portion of any configured ACE. In this example configuration, if a TCP packet destined to However, all remaining non-initial fragments are allowed by the first ACE based completely on the Layer 3 information in the packet and ACE.
This scenario is shown in this configuration:. Due to the nonintuitive nature of fragment handling, IP fragments are often inadvertently permitted by ACLs. Fragmentation is also often used in attempts to evade detection by intrusion detection systems. It is for these reasons that IP fragments are often used in attacks, and why they must be explicitly filtered at the top of any configured iACLs.
The functionality from this example must be used in conjunction with the functionality of the previous examples. IP options present a security challenge for network devices because these options must be processed as exception packets. This requires a level of CPU effort that is not required for typical packets that traverse the network. The presence of IP options within a packet can also indicate an attempt to subvert security controls in the network or otherwise alter the transit characteristics of a packet.
It is for these reasons that packets with IP options must be filtered at the edge of the network. This example must be used with the ACEs from previous examples in order to include complete filtering of IP packets that contain IP options:. The TTL value of an IP datagram is decremented by each network device as a packet flows from source to destination.
Although initial values vary by operating system, when the TTL of a packet reaches zero, the packet must be dropped. The device that decrements the TTL to zero, and therefore drops the packet, is required in order to generate and send an ICMP Time Exceeded message to the source of the packet.
The generation and transmission of these messages is an exception process. Routers can perform this function when the number of IP packets that are due to expire is low, but if the number of packets due to expire is high, generation and transmission of these messages can consume all available CPU resources. This presents a DoS attack vector. It is for this reason that devices need to be hardened against DoS attacks that utilize a high rate of IP packets that are due to expire.
It is recommended that organizations filter IP packets with low TTL values at the edge of the network. Completely filtering packets with TTL values insufficient to traverse the network mitigates the threat of TTL-based attacks. This provides protection against TTL expiry attacks for networks up to five hops in width. Note : Some protocols make legitimate use of packets with low TTL values.
Management sessions to devices allow you the ability to view and collect information about a device and its operations. If this information is disclosed to a malicious user, the device can become the target of an attack, compromised, and used in order to perform additional attacks.
Anyone with privileged access to a device has the capability for full administrative control of that device. It is imperative to secure management sessions in order to prevent information disclosure and unauthorized access. This allows the administrator additional control over a device and how the device is accessed. In addition, CPPr includes these additional control plane protection features:. CPPr allows an administrator to classify, police, and restrict traffic that is sent to a device for management purposes with the host subinterface.
Examples of packets that are classified for the host subinterface category include management traffic such as SSH or Telnet and routing protocols. Because information can be disclosed in an interactive management session, this traffic must be encrypted so that a malicious user cannot gain access to the data that is transmitted. Traffic encryption allows a secure remote access connection to the device.
If the traffic for a management session is sent over the network in cleartext, an attacker can obtain sensitive information about the device and the network. Cisco IOS software also supports the Secure Copy Protocol SCP , which allows an encrypted and secure connection in order to copy device configurations or software images. SSH runs on top of a reliable transport layer and provides strong authentication and encryption capabilities.
SSH provides a means to securely access and securely execute commands on another computer or device over a network. SSH Version 1. SSHv1 is considered to be insecure and can have adverse effects on the system. An SSH user who tries to establish the credentials provides an encrypted signature with the private key. The signature and the user's public key are sent to the SSH server for authentication. The SSH server computes a hash over the public key provided by the user.
The hash is used in order to determine if the server has an entry that matches. If a match is found, RSA-based message verification is performed with the public key. Hence, the user is authenticated or denied access based on the encrypted signature. When the client tries to establish an SSH session with a server, it receives the signature of the server as part of the key exchange message.
If the strict host key checking flag is enabled on the client, the client checks whether it has the host key entry that corresponds to the server preconfigured. If a match is found, the client tries to validate the signature with the server host key. If the server is successfully authenticated, the session establishment continues; otherwise it is terminated and displays a Server Authentication Failed message.
The user authentication is successful if the RSA public key stored on the server is verified with the public or the private key pair stored on the client. You must be aware that console ports on Cisco IOS devices have special privileges. In particular, these privileges allow an administrator to perform the password recovery procedure.
In order to perform password recovery, an unauthenticated attacker would need to have access to the console port and the ability to interrupt power to the device or to cause the device to crash. Any method used in order to access the console port of a device must be secured in a manner that is equal to the security that is enforced for privileged access to a device.
Methods used in order to secure access must include the use of AAA, exec-timeout, and modem passwords if a modem is attached to the console. If password recovery is not required, then an administrator can remove the ability to perform the password recovery procedure using the no service password-recovery global configuration command; however, once the no service password-recovery command has been enabled, an administrator can no longer perform password recovery on a device.
In most situations, the AUX port of a device must be disabled in order to prevent unauthorized access. An AUX port can be disabled with these commands:. Interactive management sessions in Cisco IOS software use a tty or virtual tty vty. A tty is a local asynchronous line to which a terminal can be attached for local access to the device or to a modem for dialup access to a device. Note that ttys can be used for connections to console ports of other devices.
This function allows a device with tty lines to act as a console server where connections can be established across the network to the console ports of devices connected to the tty lines. The tty lines for these reverse connections over the network must also be controlled. A vty line is used for all other remote network connections supported by the device, regardless of protocol SSH, SCP, or Telnet are examples. In order to ensure that a device can be accessed via a local or remote management session, proper controls must be enforced on both vty and tty lines.
When all vty lines are in use, new management sessions cannot be established, which creates a DoS condition for access to the device. The simplest form of access control to a vty or tty of a device is through the use of authentication on all lines regardless of the device location within the network. This is critical for vty lines because they are accessible via the network.
A tty line that is connected to a modem that is used for remote access to the device, or a tty line that is connected to the console port of other devices are also accessible via the network. Other forms of vty and tty access controls can be enforced with the transport input or access-class configuration commands, with the use of the CoPP and CPPr features, or if you apply access lists to interfaces on the device. Authentication can be enforced through the use of AAA, which is the recommended method for authenticated access to a device, with the use of the local user database, or by simple password authentication configured directly on the vty or tty line.
The service tcp-keepalives-in command must also be used in order to enable TCP keepalives on incoming connections to the device. This ensures that the device on the remote end of the connection is still accessible and that half-open or orphaned connections are removed from the local IOS device. A vty and tty should be configured in order to accept only encrypted and secure remote access management connections to the device or through the device if it is used as a console server.
This section addresses ttys because such lines can be connected to console ports on other devices, which allow the tty to be accessible over the network. In an effort to prevent information disclosure or unauthorized access to the data that is transmitted between the administrator and the device, transport input ssh should be used instead of clear-text protocols, such as Telnet and rlogin.
The transport input none configuration can be enabled on a tty, which in effect disables the use of the tty line for reverse-console connections. Both vty and tty lines allow an administrator to connect to other devices.
In order to limit the type of transport that an administrator can use for outgoing connections, use the transport output line configuration command. If outgoing connections are not needed, then transport output none should be used. However, if outgoing connections are allowed, then an encrypted and secure remote access method for the connection should be enforced through the use of transport output ssh.
Note : IPSec can be used for encrypted and secure remote access connections to a device, if supported. In some legal jurisdictions, it can be impossible to prosecute and illegal to monitor malicious users unless they have been notified that they are not permitted to use the system. One method to provide this notification is to place this information into a banner message that is configured with the Cisco IOS software banner login command.
Legal notification requirements are complex, vary by jurisdiction and situation, and should be discussed with legal counsel. Even within jurisdictions, legal opinions can differ. In cooperation with counsel, a banner can provide some or all of the this information:.
From a security point of view, rather than legal, a login banner should not contain any specific information about the router name, model, software, or ownership. This information can be abused by malicious users. The Authentication, Authorization, and Accounting AAA framework is critical in order to secure interactive access to network devices. The AAA framework provides a highly configurable environment that can be tailored based on the needs of the network.
When you do not depend on a single shared password, the security of the network is improved and your accountability is strengthened. The previous configuration can be used as a starting point for an organization-specific AAA authentication template. A method list is a sequential list that describes the authentication methods to be queried in order to authenticate a user.
Method lists enable you to designate one or more security protocols to be used for authentication, and thus ensure a backup system for authentication in case the initial method fails. Cisco IOS software uses the first listed method that successfully accepts or rejects a user. Subsequent methods are only attempted in cases where earlier methods fail due to server unavailability or incorrect configuration.
The complete list of options for on-device authentication includes enable, local, and line. Each of these options has advantages. The use of the enable secret is preferred because the secret is hashed with a one-way algorithm that is inherently more secure than the encryption algorithm that is used with the Type 7 passwords for line or local authentication.
However, on Cisco IOS software releases that support the use of secret passwords for locally defined users, fallback to local authentication can be desirable. This allows for a locally defined user to be created for one or more network administrators. Refer to Configuring Authentication for more information on the use of fallback authentication with AAA. Originally designed in order to allow quick decryption of stored passwords, Type 7 passwords are not a secure form of password storage.
There are many tools available that can easily decrypt these passwords. The use of Type 7 passwords should be avoided unless required by a feature that is in use on the Cisco IOS device. The removal of passwords of this type can be facilitated through AAA authentication and the use of the Enhanced Password Security feature, which allows secret passwords to be used with users that are locally defined via the username global configuration command.
If you cannot fully prevent the use of Type 7 passwords, consider these passwords obfuscated, not encrypted. See the General Management Plane Hardening section of this document for more information about the removal of Type 7 passwords. The AAA server then uses its configured policies in order to permit or deny the command for that particular user. This configuration can be added to the previous AAA authentication example in order to implement command authorization:.
Refer to Configuring Authorization for more information about command authorization. The AAA servers that are leveraged in an environment should be redundant and deployed in a fault-tolerant manner. Refer to Deploy the Access Control Servers for more information. It is critical that SNMP be properly secured in order to protect the confidentiality, integrity, and availability of both the network data and the network devices through which this data transits.
SNMP provides you with a wealth of information on the health of network devices. This information should be protected from malicious users that want to leverage this data in order to perform attacks against the network. Community strings are passwords that are applied to an IOS device to restrict access, both read-only and read-write access, to the SNMP data on the device.
These community strings, as with all passwords, should be carefully chosen to ensure they are not trivial. Community strings should be changed at regular intervals and in accordance with network security policies.
For example, the strings should be changed when a network administrator changes roles or leaves the company. Note : The previous community string examples have been chosen in order to clearly explain the use of these strings. For production environments, community strings should be chosen with caution and should consist of a series of alphabetical, numerical, and non-alphanumeric symbols. Refer to Recommendations for Creating Strong Passwords for more information on the selection of non-trivial passwords.
This configuration restricts SNMP read-only access to end host devices that reside in the Once a view is created and applied to a community string with the snmp-server community community-string view global configuration commands, if you access MIB data, you are restricted to the permissions that are defined by the view. When appropriate, you are advised to use views to limit users of SNMP to the data that they require.
SNMPv3 provides secure access to devices because it authenticates and optionally encrypts packets over the network. SNMPv3 consists of three primary configuration options:. The engine ID can be displayed with the show snmp engineID command as shown in this example:. The next step is to configure an SNMPv3 group. Note that snmp-server user configuration commands are not displayed in the configuration output of the device as required by RFC ; therefore, the user password is not viewable from the configuration.
In order to view the configured users, enter the show snmp user command as shown in this example:. The MPP feature allows an administrator to designate one or more interfaces as management interfaces. Management traffic is permitted to enter a device only through these management interfaces.
After MPP is enabled, no interfaces except designated management interfaces accept network management traffic that is destined to the device. Event logging provides you visibility into the operation of a Cisco IOS device and the network into which it is deployed. Cisco IOS software provides several flexible logging options that can help achieve the network management and visibility goals of an organization.
These sections provide some basic logging best practices that can help an administrator leverage logging successfully while minimizing the impact of logging on a Cisco IOS device. You are advised to send logging information to a remote syslog server. This makes it possible to correlate and audit network and security events across network devices more effectively.
Note that syslog messages are transmitted unreliably by UDP and in cleartext. For this reason, any protections that a network affords to management traffic for example, encryption or out-of-band access should be extended in order to include syslog traffic. This configuration example configures a Cisco IOS device in order to send logging information to a remote syslog server:. Integrated in Messages saved on an ATA drive persist after a router is rebooted.
This configuration lines configure ,, bytes MB of logging messages to the syslog directory of the ATA flash disk0 , specifying a file size of 16, bytes:. If not, the oldest file of logging messages by timestamp is deleted, and the current file is saved.
Note : An ATA flash drive has limited disk space and thus needs to be maintained to avoid overwriting stored data. Each log message that is generated by a Cisco IOS device is assigned one of eight severities that range from level 0, Emergencies, through level 7, Debug. Unless specifically required, you are advised to avoid logging at level 7.
Logging at level 7 produces an elevated CPU load on the device that can lead to device and network instability. The global configuration command logging trap level is used in order to specify which logging messages are sent to remote syslog servers. The level specified indicates the lowest severity message that is sent.
For buffered logging, the logging buffered level command is used. This configuration example limits log messages that are sent to remote syslog servers and the local log buffer to severities 6 informational through 0 emergencies :. Refer to Troubleshooting, Fault Management, and Logging for more information. With Cisco IOS software, it is possible to send log messages to monitor sessions - monitor sessions are interactive management sessions in which the EXEC command terminal monitor has been issued - and to the console.
Instead, you are advised to send logging information to the local log buffer, which can be viewed with the show logging command. Use the global configuration commands no logging console and no logging monitor in order to disable logging to the console and monitor sessions. This configuration example shows the use of these commands:.
Cisco IOS software supports the use of a local log buffer so that an administrator can view locally generated log messages. The use of buffered logging is highly recommended versus logging to either the console or monitor sessions. There are two configuration options that are relevant when configuring buffered logging: the logging buffer size and the message severities that is stored in the buffer.
The size of the logging buffer is configured with the global configuration command logging buffered size. The lowest severity included in the buffer is configured with the logging buffered severity command.
An administrator is able to view the contents of the logging buffer through the show logging EXEC command. This configuration example includes the configuration of a logging buffer of bytes, as well as a severity of 6, informational, which indicates that messages at levels 0 emergencies through 6 informational is stored:. In order to provide an increased level of consistency when you collect and review log messages, you are advised to statically configure a logging source interface.
Accomplished via the logging source-interface interface command, statically configuring a logging source interface ensures that the same IP address appears in all logging messages that are sent from an individual Cisco IOS device. For added stability, you are advised to use a loopback interface as the logging source.
This configuration example illustrates the use of the logging source-interface interface global configuration command in order to specify that the IP address of the loopback 0 interface be used for all log messages:. The configuration of logging timestamps helps you correlate events across network devices. It is important to implement a correct and consistent logging timestamp configuration to ensure that you are able to correlate logging data.
Logging timestamps should be configured to include the date and time with millisecond precision and to include the time zone in use on the device. This example includes the configuration of logging timestamps with millisecond precision within the Coordinated Universal Time UTC zone:.
If you prefer not to log times relative to UTC, you can configure a specific local time zone and configure that information to be present in generated log messages. Such features include functionality to archive configurations and to rollback the configuration to a previous version as well as create a detailed configuration change log.
Stored manually or automatically, the configurations in this archive can be used in order to replace the current running configuration with the configure replace filename command. This is in contrast to the copy filename running-config command. The configure replace filename command replaces the running configuration as opposed to the merge performed by the copy command. You are advised to enable this feature on all Cisco IOS devices in the network. Once enabled, an administrator can cause the current running configuration to be added to the archive with the archive config privileged EXEC command.
The archived configurations can be viewed with the show archive EXEC command. This example illustrates the configuration of automatic configuration archiving. This example instructs the Cisco IOS device to store archived configurations as files named archived-config-N on the disk0: file system, to maintain a maximum of 14 backups, and to archive once per day minutes and when an administrator issues the write memory EXEC command.
Although the configuration archive functionality can store up to 14 backup configurations, you are advised to consider the space requirements before you use the maximum command. This feature helps eliminate the undesirable impact of simultaneous changes made to related configuration components. This feature is configured with the global configuration command configuration mode exclusive mode and operates in one of two modes: auto and manual. In auto-mode, the configuration automatically locks when an administrator issues the configure terminal EXEC command.
In manual mode, the administrator uses the configure terminal lock command in order to lock the configuration when it enters configuration mode. When this feature is enabled, it is not possible to alter or remove these backup files. You are advised to enable this feature in order to prevent both inadvertent and malicious attempts to delete these files. Once this feature is enabled, it is possible to restore a deleted configuration or Cisco IOS software image.
The current running state of this feature can be displayed with the show secure boot EXEC command. A digitally signed image carries an encrypted with a private key hash of itself. Upon check, the device decrypts the hash with the corresponding public key from the keys it has in its key store and also calculates its own hash of the image.
If the decrypted hash matches the calculated image hash, the image has not been tampered with and can be trusted. Digitally signed Cisco software keys are identified by the type and version of the key. A key can be a special, production, or rollover key type. Production and special key types have an associated key version that increments alphabetically whenever the key is revoked and replaced. The ROMMON image is upgradable and must be signed with the same key as the special or production image that is loaded.
This command verifies the integrity of image cuniversalk9-mz. SSA in flash with the keys in the device key store:. Refer to Digitally Signed Cisco Software for more information about this feature. Key replacement and revocation replaces and removes a key that is used for a Digitally Signed Cisco Software check from a platform's key storage. Only special and production keys can be revoked in the event of a key compromise. A new special or production key for a special or production image comes in a production or revocation image that is used in order to revoke the previous special or production key.
The revocation image integrity is verified with a rollover key that comes prestored on the platform. A rollover key does not change. When you revoke a production key, after the revocation image is loaded, the new key it carries is added to the key store and the corresponding old key can be revoked as long as ROMMON image is upgraded and the new production image is booted.
When you revoke a special key, a production image is loaded. This image adds the new special key and can revoke the old special key. This example describes revocation of a special key. A new special image cuniversalk9-mz. SSB can then be copied to the flash to be loaded and the signature of the image is verified with the newly added special key.
SSB :. The log is maintained on the Cisco IOS device and contains the user information of the individual who made the change, the configuration command entered, and the time that the change was made. This functionality is enabled with the logging enable configuration change logger configuration mode command. The optional commands hidekeys and logging size entries are used in order to improve the default configuration becuase they prevent the logging of password data and increase the length of the change log.
You are advised to enable this functionality so that the configuration change history of a Cisco IOS device can be more easily understood. Additionally, you are advised to use the notify syslog configuration command in order to enable the generation of syslog messages when a configuration change is made.
After the Configuration Change Notification and Logging feature has been enabled, the privileged EXEC command show archive log config all can be used in order to view the configuration log. Control plane functions consist of the protocols and processes that communicate between network devices in order to move data from source to destination. It is important that events in the management and data planes do not adversely affect the control plane.
Should a data plane event such as a DoS attack impact the control plane, the entire network can become unstable. This information about Cisco IOS software features and configurations can help ensure the resilience of the control plane. Protection of the control plane of a network device is critical because the control plane ensures that the management and data planes are maintained and operational. If the control plane were to become unstable during a security incident, it can be impossible for you to recover the stability of the network.
In many cases, you can disable the reception and transmission of certain types of messages on an interface in order to minimize the amount of CPU load that is required to process unneeded packets. An ICMP redirect message can be generated by a router when a packet is received and transmitted on the same interface. In this situation, the router forwards the packet and sends an ICMP redirect message back to the sender of the original packet.
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