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Originally Posted by dilbert No, all should be different. A.A.A.A - 1:1:1:1:1:1 B.B.B.B - 2:2:2:2:2:2 But, all depends what ifconfig says for your ports. To get a picture what's going ...
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  1. #11
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    Quote Originally Posted by dilbert
    No, all should be different.

    A.A.A.A - 1:1:1:1:1:1
    B.B.B.B - 2:2:2:2:2:2

    But, all depends what ifconfig says for your ports. To get a picture what's going on, the addresses from the ports gained by ifconfig need to match the values inside the ARP reply.

    Different MAC addresses for the same IP address shouldn't happen. Compare the MAC and IP addresses from the ARP reply with the output of ifconfig
    Yes i understand that it should be different.. but i see something weird.. so i'm attaching some screen shots of what i see in ethereal here.. it's what I felt was wrong..

    pic 1: the 3 packets that i received in ethereal (1 ARP request and 2 ARP replies)

    pic 2: The contents of the ARP request

    pic 3: the contents of the first ARP reply

    pic 4: the contents of the second ARP reply
    Attached Images Attached Images
    • File Type: jpg 1.JPG (24.6 KB, 10 views)
    • File Type: jpg 2.JPG (38.3 KB, 9 views)
    • File Type: jpg 3.JPG (37.2 KB, 7 views)
    • File Type: jpg 4.JPG (36.5 KB, 8 views)

  2. #12
    Linux Newbie dilbert's Avatar
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    I think the sender IP address in "2.jpg" shouldn't be 0.0.0.0. I don't know what happens if you use that IP address. At least, nobody does this, normally.

    On that sender's port, the IP should be set to an IP address that can communicate with the others in the same subnet.

    Why the replies are then sent itself, i.e., same sender, same target, I don't know, but IP address 0.0.0.0 looks to be the culprit.

  3. #13
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    Ipmi?

    Is this thread still active?

    I've encountered an eerily similar issue where an ARP query gets two replies from (apparently) the same host. In my case, I have a rack of servers, and they all behave the same way: I get the first ARP reply with the MAC of the expect ethernet interface. Then I get a second reply with a very slightly different MAC. In my case the second MAC address is the original plus two.

    This doesn't seem to affect Linux clients: they appear to disregard the second reply. But Windows clients are confused by it. For example, on Windows, when I try to ping a machine by IP address (that is not already in the ARP cache), what happens is as follows: an ARP query is sent out; when a ARP reply is received, a ping is sent to the MAC address supplied in the reply (and the ping is echoed back successfully). However, then a second ARP reply is received, and the second ping goes to the second MAC address (which in this case appears to be non-existent, so no ping echo is ever received.)

    Anyway... does this sound like your problem? I think I've figured out the cause. In my case, each of the servers has IPMI enabled on their primary ethernet port, so that I can query and power them up remotely. If I power a server down and do an ARP query for its ethernet address, it responds with the second MAC address.

    I still haven't figured out what to do about this. It all depends on how much confusion it causes Windows, and I'm currently looking into that.

    HTH,

    XOX DOM

  4. #14
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    ha.. i happened to check my mail and saw this..

    i replied cos i know how hard it is to get ppl to understand that this is a real phenomenon.. no one "believed" me when i wrote this and i didn't get any solutions to this.. ha.. but luckily, mr google helped me.. and i chanced upon this.. don't want u to go around chasing the goose..

    this is an arp flux problem (hope i didn't recall wrongly)

    look at this website:
    http://linux-ip.net/html/ether-arp.html

    you will find what you want there..


    cheers.. and hope it helps..
    your windows problem will be solved..


    Quote Originally Posted by domlayfield
    Is this thread still active?

    I've encountered an eerily similar issue where an ARP query gets two replies from (apparently) the same host. In my case, I have a rack of servers, and they all behave the same way: I get the first ARP reply with the MAC of the expect ethernet interface. Then I get a second reply with a very slightly different MAC. In my case the second MAC address is the original plus two.

    This doesn't seem to affect Linux clients: they appear to disregard the second reply. But Windows clients are confused by it. For example, on Windows, when I try to ping a machine by IP address (that is not already in the ARP cache), what happens is as follows: an ARP query is sent out; when a ARP reply is received, a ping is sent to the MAC address supplied in the reply (and the ping is echoed back successfully). However, then a second ARP reply is received, and the second ping goes to the second MAC address (which in this case appears to be non-existent, so no ping echo is ever received.)

    Anyway... does this sound like your problem? I think I've figured out the cause. In my case, each of the servers has IPMI enabled on their primary ethernet port, so that I can query and power them up remotely. If I power a server down and do an ARP query for its ethernet address, it responds with the second MAC address.

    I still haven't figured out what to do about this. It all depends on how much confusion it causes Windows, and I'm currently looking into that.

    HTH,

    XOX DOM

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