I saw a strange situation at one of our customers. Platform is Cisco 1760 running 12.2.2.XK2, attached to a hub(100Mbps). There are two clients on the ethernet. This 1760 is attached to the head office with 64Kbps Leased line. The client can ping the head office and can start AS/400 session, but can not be pinged by any other clients(in head office), servers and even by its gateway(c1760). The client can be seen in the output of "show arp" in the gateway Cisco 1760 but can not be pinged at all. But this client can ping its gateway. At the same time i can see some traffic on serial port ( by sh int serial x/y) but can see only the following rows in the "show interface Fastethernet0/0" command:
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
but input packet and output packet numbers are increasing.
Do you have any idea, what is happening to this router?
Make sure that the arp entries in the gateway router (for the client) and client (for the gateway) are showing the correct MAC addresses. That will eliminate dup addresses. Then verify the masks in the router and client.
in fact there is only one online client now. and there is no ip address duplication. ip addresses, subnet masks and mac addresses are all correct. but now i'm going to get an other client into LAN and will check if it can pings the neighbour client. any other idea?
Start with the 1760 gateway and the client. Until that work no one else will be able to reach it. A few things to try.
sh ip route x.x.x.x in the 1760 using the clients ip addr. see if it is really using the right port.
turn on ""debug ip packet detail" in the 1760 then ping the client. watch for encapsulation errors and which port the packet is going out. Watch for return traffic. You said there is only one client so I'm not detailing how to narrow down the debug output.
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