Virtual Terminal Access Lists

You can provide additional security for your router by using access lists to restrict access to vty lines.

When the router attempts to authenticate a user, it always selects the first vty line that has an access class that permits that user’s host. The vty line’s configuration must authenticate the user to allow access. Otherwise, the user can never gain access. Consequently, we recommend that you use identical authentication configurations for all vtys that have the same access class list.

To set up access lists:

• Associate the access list with inbound Telnet sessions.

  host1(config)#line vty 12 15

  host1(config-line)#access-class Management in

• Configure an access list.

  host1(config)#access-list Management permit ip 192.168.11.16 0.0.0.15 any

  host1(config)#access-list Management permit ip 192.168.4.0 0.0.0.255

  host1(config)#access-list Management deny ip any any

access-class in

• Use to associate the access list with vty lines.
• Example—This example sets the virtual terminal lines to which you want to restrict access and specifies an access class to grant access to incoming requests.

  host1(config)#line vty 12 15

  host1(config-line)#access-class Management in

• Use the no version to remove access restrictions.
• See access-class in.

access-list

• Use to configure an access list.
• Example

  host1(config)#access-list Management permit ip 192.168.11.16 0.0.0.15 any

• Use the no version to remove the access list.
• See access-list.

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