Cisco IOS Cookbook, 2nd Edition

Setting Up Frame Relay with Map Statements

Problem

You want to configure Frame Relay services so that every PVC appears to share the same interface.

Solution

In its simplest form, the Frame Relay map configuration involves considerably less typing than the subinterface version of the same configuration:

Central#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Central(config)#interface Serial0
Central(config)#description Frame Relay to branches
Central(config-if)#ip address 192.168.1.1 255.255.255.0
Central(config-if)#encapsulation frame-relay
Central(config-if)#frame-relay map ip 192.168.1.10 101
Central(config-if)#frame-relay map ip 192.168.1.11 102
Central(config-if)#frame-relay map ip 192.168.1.12 103
Central(config-if)#exit
Central(config)#end
Central#

Discussion

Instead of treating the Frame Relay WAN as a series of point-to-point logical connections as we did in Recipe 10.1, you can set configure it to look similar to a LAN segment with a contiguous block of IP addresses. There are two ways to do this—either by using frame-relay map statements, as in this recipe, or using multipoint subinterfaces, as in Recipe 10.4. In general, we prefer to use point-to-point subinterfaces for Frame Relay networks because it gives you more detailed controls over the routing protocol.

Furthermore, when you use point-to-point subinterfaces, the router can generate a trap when a DLCI becomes inactive, which makes network management much easier. With multipoint subinterfaces, ...