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ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

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  • 1.  ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

    Posted Jun 27, 2014 04:50 AM

    Hello,

     

    First I would like to thanks this community because I've used it to find many solutions since nearly ten years now.

     

    Now I'm facing a network issue for wich I can't find any information here (or via googling it).

     

    On a LAN of nearly 100 computers, I have 2 computers which suddenly can't contact each other (ping/tcp/udp), but it was working for weeks.

     

    The network topology :

     

    computer A ---- switch9 (2510-48) ---- router (OmniSwitch 6850) ---- switch10 (2510-48) ---- computer B

     

    computer A 192.168.2.101

    computer B 192.168.2.140

     

    router 192.168.2.254

     

    After wiresharking from computer B, I can see that B never ask for A's MAC address, and when A is asking for B's MAC address, B does not respond.

     

    A and B can contact all others computer on this network (and on routed networks).

     

    show arp on switch10 (after ping on A & B)

    IP ARP table

    IP Address MAC Address Type Port
    --------------- ----------------- ------- ----
    192.168.2.22 b8ac6f-1226e1 dynamic 49
    192.168.2.100 0026b9-8d77cf dynamic 49
    192.168.2.101 0026b9-8e5abf dynamic 49
    192.168.2.109 90b11c-a7b2d4 dynamic 49
    192.168.2.140 ecf4bb-1df730 dynamic 13
    192.168.2.183 002219-162b50 dynamic 49
    192.168.2.254 00e0b1-b74c90 dynamic 49

     

    show arp on switch9

    IP ARP table

    IP Address MAC Address Type Port
    --------------- ----------------- ------- ----
    192.168.2.22 b8ac6f-1226e1 dynamic 49
    192.168.2.100 0026b9-8d77cf dynamic 49
    192.168.2.101 0026b9-8e5abf dynamic 25
    192.168.2.140 ecf4bb-1df730 dynamic
    192.168.2.254 00e0b1-b74c90 dynamic 49

     

    As you can see, switch9 know B's mac-address but it is not associated with any port on the switch.

     

    It seems that switch9 not properly learn B's mac address, but I can ping B from switch9.

    I've done a show mac-address on switch9, but B's mac address was not listed (A's one was).

     

    Any help would be greatly appreciated.

     

    Regards.


    #ARP


  • 2.  RE: ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

    Posted Jul 30, 2014 08:08 AM

    I've reloaded switch9, it has solved the problem.