frame relay

on a Cisco router there two possibilieties to configure frame relay:

1. static (using framerelay map and point to point subinterfaces)
2. dynamic (using inverse arp)

Simpliest is inverse arp based configuration. inverse arp is responsible for mapping next hop ip addresses to correct DLCIs. inverse arp is enabled by default.

inverse arp on point to multipoint subinterface:

!

interface Serial0/0.2 multipoint

ip address 10.1.13.1 255.255.255.0

no ip route-cache

frame-relay interface-dlci 102

frame-relay interface-dlci 103

!

R1_pod2#sho frame-relay map

Serial0/0.2 (up): ip 10.1.13.2 dlci 102(0x66,0x1860), dynamic,

broadcast,, status defined, active

Serial0/0.2 (up): ip 10.1.13.3 dlci 103(0x67,0x1870), dynamic,

broadcast,, status defined, active

R1_pod2#

Static mapping involves permanent assigments of next hop ip addressess to DLCI values. It is possible to use static mapping on interfaces where inverse arp is used.

!

interface Serial0/1/0.1 multipoint

ip address 10.1.13.3 255.255.255.0

frame-relay map ip 10.1.13.1 301

frame-relay map ip 10.1.13.2 302

frame-relay interface-dlci 301

frame-relay interface-dlci 302

no frame-relay inverse-arp

!

Very important is LMI status messages. by default they send every 10 sec. default behaviour can be changed using:

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#int ser 0/1/0

R3(config-if)#

R3(config-if)#keepalive 6

R3(config-if)#^Z

R3#