Inverse ARP doesn't work

Unanswered Question
Dec 20th, 2009


I have 2 routers connected through the Frame Relay switch. On the first router (R1) I'd like to use static DLCI-IP mapping, but on the second (R2) I'd like to use Inverse ARP. Inverse ARP doesn't work. Output of 'show frame-relay map' is empty.

I've attached the scheme and parts of configs.

Could you please help me find the issue?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Paolo Bevilacqua Sun, 12/20/2009 - 04:36

Why don't you use point-to-point subinterfaces instead and so eliminate all needs for confusing and obsolete configurations.

kondratev Sun, 12/20/2009 - 07:52

Unfortunately (there is a weighty reason) I must use multipoint interfaces.

Paolo Bevilacqua Sun, 12/20/2009 - 08:00

And what would be the weigthy reason ?

Probably not heavvier than having unrealible, obscure rotuer configuration.

Giuseppe Larosa Sun, 12/20/2009 - 07:38

Hello Kondratev,

inverse ARP works based on the fact the the remote DTE (R1 in your case) cooperates by sending frames that travel on the PVC telling "Hi at the other side of this PVC there is my interface and my address is x.x.x.x".

Now, you have only two DTE on a point-to-point PVC. On R1 you have configured the interface with:

frame-relay map ip 132
no frame-relay inverse-arp

the second command does not tell R1 to ignore inverse ARP messages coming from R2 but tells R1 to suppress its own messages.

As a result of this R2 is waiting for inverse ARP messages that will never come.

To be noted the FR switch has no role in this: its job ends when it switches FR frames from one port to the other port it does not take part in inverse ARP process.

So if you want to build a working example of inverse ARP you need to have it enabled on both DTE at the two ends of the PVC or move the frame-relay map command on R2 side


Hope to help


Giuseppe Larosa Sun, 12/20/2009 - 09:13

Hello Kondratev,

post a sh frame-relay map taken on R2 in the new scenario.

you may want to consider to use point to multipoint subinterfaces

Hope to help


Giuseppe Larosa Sun, 12/20/2009 - 11:44

Hello Kondratev,

I would try to use frame-relay route on the FR switch, I've never used the connect command.

With frame relay route you give two commands one under serial1 and one under serial2

int ser1

enc frame-rel

frame-rel intf-type dce

frame-relay route 132 int ser2 231

int ser2

enc frame-rel

frame-rel intf-type dce

frame-relay route 231 int ser1 132

this is the kind of FR switch I've used in the past

Hope to help



This Discussion