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.
