Technical data

Routing across Modem Lines 6-5
Configuring the Dialing Access Server
Step 4 Require login authentication on VTY lines 0 through 4. The login authentication default
command uses the aaa authentication default local authentication list. The local
keyword means that the local username database will be used for security. On this access
server, only five VTY lines have been defined.
Snoopy(config-if)# line vty 0 4
Snoopy(config-line)# login authentication default
Step 5 Create access list filters. In this example, the packets that the access list permits are
referenced by the dialer-list command (in Step 6 of this procedure) to determine
interesting packets.
Snoopy(config-line)# exit
Snoopy(config)# access-list 100 deny ip 0.0.0.0 255.255.255.255 255.255.255.255
0.0.0.0
Snoopy(config)# access-list 100 permit ip 0.0.0.0 255.255.255.255 0.0.0.0
255.255.255.255
In the preceding access-list command, the number 100 is the list identifier. All access-list
commands with the same identifier define a single filter. Ordering of the access-list
commands is very important. Statements in an access list are parsed one by one until a
match is found. After a match is found, any access list definitions that follow are ignored.
Although it is not displayed, an implicit “deny all” statement is always appended to the
end of an access list. Therefore, if a packet reaches the end of an access list without
matching a permit statement, the packet is denied automatically.
The line access-list 100 deny ip 0.0.0.0 255.255.255.255 255.255.255.255
0.0.0.0 specifies that all broadcast packets are uninteresting. Specifically, RIP updates
cannot initiate a call, nor can they reset the dialer idle-timeout counter in this example.
The line access-list 100 permit ip 0.0.0.0 255.255.255.255 0.0.0.0
255.255.255.255 specifies that all other IP packets are interesting.
Step 6 Reference the filter defined by access list 100. Packets permitted by access list 100 are
considered interesting packets for a DDR interface belonging to dialer group 1.
Snoopy(config)# dialer-list 1 list 100
You have configured the answering access server (Snoopy). At this point, you can configure the
dialing access server (Woodstock).
Configuring the Dialing Access Server
In this configuration, the dialing access server has the name Woodstock. This name is passed by this
access server during the PPP authentication process, in the same way that the answering access
server’s name is authenticated. (Refer to the section “Configuring Security for the Dialing Access
Server.”)
Note Names are case sensitive, so be sure that both the dialing and answering access servers use
the same capitalization and spelling.
Perform the steps in the following procedures to configure the access server that initiates the call
(Woodstock). The configuration is broken into components (routing in global configuration mode,
the Ethernet interface, asynchronous interfaces, security, and so on).