After spending way too much time troubleshooting my frame switch, I figured my advice could help others. In my case, I had a very, VERY weird issue with my frame switch, which essentially manifested itself in the form of one-way communciation between the devices connected to it. The interfaces would come up for 30 seconds, and drop. The frame switch never saw them up. The configs were right..they were dead on. Tried switching to PPP, or HDLC encapsulation..nothing. Swapped cables…nothing. Swapped ports..nothing. Even moved modules on the routers to check for a bad slot..nothing. In the end, after several reboots, the problem disappeared. Anyways, here’s some areas to check..

• Check your frame switch config first. It should essentially be the following:

interface Serial3                                                               
description **INTERFACE TO R3 S1/0**                                           
no ip address                                                                  
encapsulation frame-relay                                                      
serial restart-delay 0                                                         
clockrate 64000                                                                
frame-relay lmi-type cisco    // Not necessarily required, but I like to do it just to know what’s going on. You can also disable frame-relay inverse-arp to be safe.                                                    
frame-relay intf-type dce                                                      
frame-relay route 301 interface Serial1 103                                    
frame-relay route 304 interface Serial4 403

Most people’s problem are going to come from the frame-relay route statement. Here’s how it breaks down:

frame-relay route <INCOMING DLCI> <OUTGOING INTERFACE> <OUTGOING DLCI>

So here’s the logic..think of it like you are the INTERFACE. So, for example, I would say “I am Serial3, and I’m connected to R3. If I receive any data on incoming DLCI 304, send it out interface Serial4 via DLCI 403. This would look like:

frame-relay route 304 interface Serial4 403

Now, as far as the router config on the other end..you just need a couple of things, the frame encap, IP, no shut, and that’s about it..if you’re getting a down/down, you need to check elsewhere.

Getting your cables straight:

• The FR switch should be the DCE for both layer 1 and layer 2. Your DB-60 DTE/DCE cables are labeled which end is DCE, and which is DTE. Make sure your DCE is inserted on the frame relay switch end..and inserted properly. It’s pretty easy to insert the cable upside down, but it won’t get a good connection, so be sure to check this.
• If you still have no luck, swap serial cables..if you have the same results, try a different port (on both ends)
• If you decide to switch interfaces on the frame switch, remove your old config on the old interface. If you do a “show frame pvc”, you’ll see two entries for that same DLCI, which could cause issues. Better safe than sorry.
• Finally, if you’re at a complete loss, unplug all other cables going into the frame switch, and blow out all config, and go one at a time. It’s best to keep it simple. Once you’ve verified your config is good to go on one interface, then you can duplicate that config on the other interfaces.

Best of luck. Hoped to have help a little. Just my $.02 after configuring my frame switch.