I am running about 30 1721 routers with T1 WICs and 12.2(13)T IOS. Generally they run without a hitch. However, I have noticed that every now and then the routers stop "talking" to other hosts via the FastEthernet0 interface. When this happens the interface shows as up/up and I can ping the IP of the interface itself but nothing else connected to that interface is pingable. At first I would reboot them to fix the problem. Lately, after a bit of troubleshooting I have found that clearing the ARP table fixes the problem right away without having to reboot. When the problem happens the ARP table has entries in it that look OK. Remote subnets reachable with the T1 are also OK but Fastethernet0 reachable addresses, machines connected to the SAME switch as the router are not pingable.
I would recommend to check for the logged messages when this happen. Also is there is chance that somebody configure the Ip address of the routers? You also said that you have 30 routers this happen in all the routers? You said also that from the routers you were not able to ping hosts.. what about the other way around???
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interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...