Technical data

Routing across Modem Lines 6-3
Configuring the Answering Access Server
Step 4 Configure a second static route, because the asynchronous interface is unnumbered (refer
to the section “Configuring the Asynchronous Interface Answering the DDR Call”). A
second static route is needed to tell the local access server (Snoopy) which interface to
use to get to the device at address 172.16.20.1. A mask of 255.255.255.255 is used to
specify that this route is a host address.
Snoopy(config)# ip route 172.16.20.1 255.255.255.255 async1
Configuring Ethernet Interface 0
Perform the following task to configure Ethernet interface 0 on the access server answering
incoming DDR calls (Snoopy):
Assign an IP address to Ethernet interface 0:
Snoopy(config-router)# interface Ethernet0
Snoopy(config-if)# ip address 172.16.10.1 255.255.255.0
Configuring the Asynchronous Interface Answering the DDR Call
Perform the following steps to configure the asynchronous interface answering DDR calls (Snoopy):
Step 1 Configure the asynchronous interface through which you need to accept a call as IP
unnumbered to conserve IP addresses and assign the IP address for Ethernet interface 0
to it.
Snoopy(config-if)# interface Async1
Snoopy(config-if)# ip unnumbered Ethernet0
Step 2 Encapsulate PPP on the interface.
Snoopy(config-if)# encapsulation ppp
Step 3 Specify asynchronous dynamic routing on the interface. The async dynamic routing
command allows routing protocols to be run over the asynchronous interface to resolve
IP routes dynamically. If the command is omitted, static routes can still be used.
Snoopy(config-if)# async dynamic routing
Step 4 Specify the IP address of the opposite access server’s (Woodstock’s) Ethernet 0 interface
as the default IP address:
Snoopy(config-if)# peer default ip address 172.16.20.1
Step 5 Configure the asynchronous interface as dedicated to PPP mode, which means that the
access server automatically uses a PPP session for this interface, and that the user will not
see an EXEC prompt. The async mode dedicated command enables the configured
session type to start automatically when the DDR link comes up.
Snoopy(config-if)# async mode dedicated
Step 6 (Optional) Configure DDR support on the asynchronous interface using the dialer
in-band command.
Snoopy(config-if)# dialer in-band