Simple Sub-interface Question

[andrewburridge]

Hey guys,

I'm just trying to get a simple setup working, basically OSPF across a few routers.  The routers are connected via serial links, with sub-interfaces set up on both routers.

All I've done so far is bring up the physical serial interfaces on both routers, create the sub-interfaces on each, and give them an ip address.  So the config for each is as follows:

Router 1

interface Serial0/0

no ip address

no fair-queue

clock rate 2000000

!

interface Serial0/0.12 point-to-point

ip address 10.1.1.1 255.255.255.252

!

Router 2

interface Serial0/0

no ip address

no fair-queue

clock rate 2000000

!

interface Serial0/0.12 point-to-point

ip address 10.1.1.2 255.255.255.252

!

I cannot ping across the link.  So my question is, what are the pre-requisites on the physical interface, and logical sub-interfaces to just get this simple setup working?  Do I need frame relay or PPP?

The interface statuses are as follows:

R1#sho ip int brief

Interface                       IP-Address           OK?      Method           Status                          Protocol

FastEthernet0/0            unassigned      YES           unset            administratively down      down

Serial0/0                       unassigned      YES           unset            up                                 up

Serial0/0.12                  10.1.1.1           YES           manual          up                            up

FastEthernet0/1            unassigned      YES           unset            administratively down      down

Serial0/1                       unassigned      YES           unset            administratively down      down

Thanks for any help!

[cadet alain · Accepted solution]

Hi,

The only way to get a  frame-relay DTE-DTE connection is to disable LMI on interface with the no keepalive command

and to use same DLCI on each side.

Otherwise you'll need a Frame-relay switch between the 2 or do a hybrid back-to-back connection.

Regards.

Alain.

[mtsb]

Can you get the output of "show frame map" when you are not able to ping? Did you configure "frame-relay switching" on both routers? Better to configure under one of the interface as dce by using "frame-relay intf-type dce" command. If you really want a self ping also to work you will have to configure and "frame-relay map ip "

Thanks,

Madhu

[cadet alain]

Hi Madhu,

If you really want a self ping also to work you will have to configure 
and "frame-relay map ip  "

Not needed for a point-to-point subinterface

Regards.

Alain.

[mtsb]

You can refer to following cco link which has configuration examples of most of commonly used frame-relay topologies.

http://www.cisco.com/en/US/tech/tk713/tk237/tech_configuration_examples_list.html

[andrewburridge]

All sorted now, thanks for your help guys!