frame relay

Unanswered Question
Mar 15th, 2007

Hi all, I was looking at my book yesterday on frame relay, is it right that if you congigure it on a serial interface ie s0, you only need to put the encapsulation in if it supports inarp? can we do this if we have multiple dlci's or would we have to use the frame interface dlci command on each instance of a sub interface ?

I have this problem too.
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CSCO10892433 Thu, 03/15/2007 - 06:22

Hi, carl

For your first question, inverse arp only works on routers that have a direct PVC between them . For those who don't have direct PVC (like spoke routers in a hub-n-spoke topology), you will need to configure a static frame-relay map. For example, R1 has one PVC connected to R2 and another PVC connected to R3, but R2 and R3 have no PVC to directly connect them. To establish ip connectivity between them, the following commands is needed:

on R2

frame-relay map ip R3-ip-address R2-dlci

on R3

frame-relay map ip R2-ip-address R3-dlci

The other way to configure full ip connectivity is use the point-to-point sub-interfaces. Configure ip address on each sub-interface and assign the correct dlci to it. Then you should have ip connectivity to the router on the other end of this PVC. Notice that each subinterface is on different sunet from others, so you will need to enable routing protocol (or use static route) to make full ip connectivity between them. A sample configuration is like below:

int s0.1 point-to-point

ip address 10.1.1.1 255.255.255.252

frame-relay interface-dlci 102

int s0.2 point-to-point

ip address 10.1.1.5 255.255.255.252

frame-relay interface-dlci 103

router rip

network 10.0.0.0

Or, you can have mixed configuration of this two kind. Some subinterfaces is point-to-point and the others use point-to-multipoint. The configuration of point-to-multipoint subinterfaces is the same as that of physical interfac except that it is on the sub-interface.A sample configuration is like below:

int s0.1 point-to-point

ip address 10.1.1.1 255.255.255.252

frame-relay interface-dlci 102

int s0.2 multipoint

ip address 10.1.1.129 255.255.255.128

frame-relay map ip 10.1.1.130 103 broadcast

frame-relay map ip 10.1.1.131 104 broadcast

HTH

SSLIN

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