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I have two Cisco 2901 GWs, each has an HWIC-2T interface module. I want to set them up back-to-back to send network traffic between PCs and Phones connected to my GWs over this link.

I have CAB-SS-X21FC (DCE) and CAB-SS-X21MT (DTE) cables connected together, then connected to Serial0/2/0 on each GW.

This is the config I have so far...


configure terminal
frame-relay switching
interface Serial 0/2/0
  encapsulation frame-relay
  frame-relay intf-type dce
  ip address
  frame-relay interface-dlci 101

(have tried adding clock rate too, although not sure what clock speed to include)


configure terminal
interface Serial 0/2/0
  encapsulation frame-relay
  ip address
  frame-relay interface-dlci 101

I then try and ping from GW1 (and vice versa) but no luck.

Am I missing some config items? Also, what is the best way to check if I am getting connectivity (i.e. a debug setting on the router)

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up vote 0 down vote accepted

First off, if this is truly a point-to-point interface, there's absolutely no reason to use frame-relay encapsulation. Either let the interfaces default to hdlc or set "encapsulation ppp" for a much simpler config.

The best way to see if these are working is the "show interface" command. "show interface brief" will list all of your interfaces in a table.

If this has to remain a frame-relay interface, use the various "show frame-relay" commands (show frame-relay map, show frame-relay lmi, etc) to see if LMI and frame-relay control messages are being properly sent and received.

More info can be found here:

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In a frame-relay back-to-back set up I think the OP needs to disable LMI and configure one end as the clock source, no? – joeqwerty Sep 27 '12 at 18:44
I disabled FR and used HDLC. I made sure I set the clock speed on the DCE router only (thanks joequerty) and it all started working. Thanks for your help – Ian Oct 11 '12 at 13:27

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