Sample Legacy DDR Configurations
One common application for DDR is a dial-up connection to the Internet. Here’s a configuration that dials an ISP any time there is traffic that needs to go to the Internet:
! Define the chat scripts chat-script modem1 "" "atz\r" OK "atdt \T" TIMEOUT 30 CONNECT \c chat-script login1 TIMEOUT 20 login: "bob\r" password: "mypassword\r" ! ! Set up the dialer interface interface async1 ! We are going to let the router negotiate its IP address through PPP ip address negotiated encapsulation ppp ! Enable dialing on this interface dialer in-band ! Set the idle timeout dialer idle-timeout 600 ! Map our provider's IP address dialer map 220.127.116.11 modem-script modem1 system-script login1 14105551212 dialer-group 2 ! ! Assign the dialer group to an access list dialer-list 2 list 101 access-list 101 permit ip any any ! ! Set a default route ip route 0.0.0.0 0.0.0.0 async1
In some respects, this is a simpler configuration than the previous one. We use a negotiated IP address (i.e., an address assigned to us by the ISP) rather than specifying the address explicitly. We specify PPP encapsulation, but don’t do any special authentication; authentication is handled by a simple login sequence, which we implement in the chat scripts. This is typical of many ISP connections.
This configuration uses a few newer features of IOS. First, we have separated the chat script into two parts, a modem script and a system script, both of which are specified in our dialer map. This ...