You might have a request in the Core Knowledge, Troubleshooting, or the Configuration section to have a Cisco router be able to PING its own Frame-Relay IP address. In this blog post, we will make sure we can accomplish this. Here is the topology that we will use:
The first order of business here is to ensure that R5 can PING the remote device of R3.
The first order of business here is to ensure that R5 can PING the remote device of R3.
Rack9R5#ping 173.9.0.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 173.9.0.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 56/58/60 ms Rack9R5#Excellent! Now let us see if R5 can PING itself. I am hoping this fails or it is going to be my shortest blog post ever! :-p
Rack9R5#ping 173.9.0.5 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 173.9.0.5, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) Rack9R5#OK. As expected, it does not work. But why? Well, let us debug frame-relay packets and see if we can determine why.
Rack9R5#debug frame-relay packet Frame Relay packet debugging is on Rack9R5#ping 173.9.0.5 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 173.9.0.5, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) Rack9R5# Dec 2 14:05:50.399: Serial0/0/0:Encaps failed--no map entry link 7(IP) Dec 2 14:05:52.399: Serial0/0/0:Encaps failed--no map entry link 7(IP) Dec 2 14:05:54.399: Serial0/0/0:Encaps failed--no map entry link 7(IP) Dec 2 14:05:56.399: Serial0/0/0:Encaps failed--no map entry link 7(IP) Dec 2 14:05:58.399: Serial0/0/0:Encaps failed--no map entry link 7(IP) Rack9R5#There is the answer. Frame-Relay does not know what DLCI to use for this destination IP address. We need to add a Frame-Relay mapping for our own IP address pointing to the DLCI of our neighbor.Let us do that now and then perform our verifications:
Rack9R5#conf t Enter configuration commands, one per line. End with CNTL/Z. Rack9R5(config)#int s0/0/0 Rack9R5(config-if)#frame map ip 173.9.0.5 503 Rack9R5(config-if)#do sh run int s0/0/0 Building configuration... Current configuration : 198 bytes ! interface Serial0/0/0 ip address 173.9.0.5 255.255.255.0 encapsulation frame-relay frame-relay map ip 173.9.0.5 503 frame-relay map ip 173.9.0.3 503 broadcast no frame-relay inverse-arp end Rack9R5(config-if)#do ping 173.9.0.5 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 173.9.0.5, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 116/118/124 msWould I engage in this extra configuration unless I was asked to do so in the exam? No way…but at least now we fully understand this under-documented little nuance.
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