You can use access lists to be more specific about what is interesting traffic. In the preceding
examples, we set the dialer list to allow any IP traffic to bring up the line and keep it up.
That’s great if you are testing, but it can defeat the purpose of why you use a DDR line in
the first place. You can use extended access lists to set the restriction, for example, to only
e-mail or Telnet.
Here is an example of how you define the dialer list to use an extended access list:
804A(config)#dialer-list 1 protocol ip list 110
804A(config)#access-list 110 permit tcp any any eq smtp
804A(config)#access-list 110 permit tcp any any eq telnet
804A(config)#int bri0
804A(config-if)#dialer-group 1
In the previous example, you configure the dialer-list command to look at an IP extended
access list. This doesn’t have to be IP; it can be used with any protocol. Create your dialer list and
then apply it to the BRI interface with the dialer-group command.
889