You just cannot assume anything when you sit for your Version 4.0 CCIE R&S Lab Exam. One of the former assumptions we could make with Version 3.x was that our Frame Relay Switch is going to be just fine and dandy. Therefore, if you examined your PVC health (status) and you saw DELETED, you could immediately inspect your Frame Relay map statements, or your frame-relay interface-dlci commands for a typo in the DLCI.

But in this new exam (Troubleshooting section or Configuration section), nothing is off limits from your problem scope. OK, well, to be more accurate, most Layer 1 issues are still indeed out of scope. In fact, in the Troubleshooting section, Layer 1 really cannot be an issue since the devices we are troubleshooting are actually virtual routers. You cannot even run up against a bad cable there! But still, there is a lot more that we can be asked to troubleshoot than in the past. And if you think about the Core Knowledge section, they could even ask Layer 1 troubleshooting-related questions there instead!

In this blog post (dedicated to my current Advanced Troubleshooting Bootcamp Live Class), we will examine Frame Relay troubleshooting where the Frame Relay Switch rears its rather ugly head.


I am going to carefully configure the R1 and R2 interfaces for Frame Relay in this scenario. I am going to “slow down to speed up” in these configurations and make sure they are letter for letter perfect. First, R1 and then R2:


R1(config)#interface serial 0/1
R1(config-if)#encapsulation frame-relay
R1(config-if)#no frame-relay inverse-arp
R1(config-if)#ip address
R1(config-if)#frame-relay map ip 102 broadcast
R1(config-if)#no shutdown
Mar  2 14:54:33.156: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1, changed state to up


Rack8R2(config)#interface serial0/1
Rack8R2(config-if)#encapsulation frame-relay
Rack8R2(config-if)#no frame-relay inverse-arp
Rack8R2(config-if)#ip address
Rack8R2(config-if)#frame-relay map ip 201 broadcast
Rack8R2(config-if)#no shutdown
Mar  2 14:59:23.362: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1, changed state to up

So far so good!I am thrilled to see the magic UP/UP system messages and I am ready to rock with a PING test.


Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 0 percent (0/5)

Not what I want to see! Let me do some further information gathering:

Rack8R2#show frame-relay pvc

PVC Statistics for interface Serial0/1 (Frame Relay DTE)

 Active     Inactive      Deleted       Static
 Local          0            0            1            0
 Switched       0            0            0            0
 Unused         0            0            0            0


Wait a minute! DELETED???? I triple-checked my DLCI configuration per the diagram. Can I access the device connecting these routers (R3 in my case)? I sure can…let me view the relevant configuration on the device.

Rack8R3#sh run
hostname Rack8R3
frame-relay switching
interface Serial1/2
 no ip address
 encapsulation frame-relay
 clock rate 64000
 frame-relay intf-type dce
interface Serial1/3
 no ip address
 encapsulation frame-relay
 clock rate 64000
 frame-relay intf-type dce

It looks like someone made a nice attempt at the Frame Relay Switch configuration here (note the highlighted commands), but they have forgotten the “static routes” for PVC switching on the device.

Rack8R3(config)#interface serial 1/2
Rack8R3(config-if)#frame-relay route 102 interface serial 1/3 201
Rack8R3(config)#interface serial 1/3
Rack8R3(config-if)#frame-relay route 201 interface serial 1/2 102

Now, drum roll please, let us try that PING again.


Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/61 ms

Now that is more like it!!!!!

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9 Responses to “Frame Relay Troubleshooting – the Frame Switch”

  1. Eric says:

    Thanks for this great blog post Anthony!

  2. martijn says:

    Would the ‘connect xyz Serial1/2 102 Serial 1/3 201′ be an option?

  3. Nadeem Rafi says:

    Nice article. For those who are using dynamips, and emulating a router as frame-relay switch, their hard work is paid off in new V4.

  4. Jeff says:

    Same goes for those that built a home/personal lab. It seems rediculous that they’d find testing an IOS frame relay switch configuration as a relevant topic these days, I’d welcome (with open arms) seeing something along these lines in the troubleshooting or config sections of the lab exam!

  5. Matt says:

    Yes the ‘connect’ is a viable option here. Both the L2 ‘connect’ statement and frame-relay route accomplish the same thing.

  6. Nick says:

    I would love to have a frame relay switch problem in the lab, easy points!

  7. Great job, this helped me more than you will know. Thanks.

  8. Shaggy says:

    Great document, this hellped me a lot


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