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I have two Linux hosts that I am trying to connect. Each host has 4 NICs. They have each been auto-configured with 169.XXX.XXX.XXX addresses. The interfaces on each are up ...
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    Can't ping via direct connection using auto-ip address


    I have two Linux hosts that I am trying to connect. Each host has 4 NICs. They have each been auto-configured with 169.XXX.XXX.XXX addresses. The interfaces on each are up and operational. I can arping the peer from either host just fine. Getting back replies.

    However, regular ping fails in both directions. I suspect it is a routing issue since ping works at layer 3 vs arping which works at layer 2. Just not sure what I am missing.

    Here are my routes:

    Host #1
    ======
    # ip route show
    default dev eth0
    169.254.0.0/16 dev eth0 src 169.254.184.195
    169.254.0.0/16 dev eth1 src 169.254.197.39
    169.254.0.0/16 dev eth2 src 169.254.184.155
    169.254.0.0/16 dev eth3 src 169.254.106.224

    Host #2
    ======
    # ip route show
    default dev eth0
    169.254.0.0/16 dev eth0 src 169.254.249.230
    169.254.0.0/16 dev eth1 src 169.254.113.198
    169.254.0.0/16 dev eth2 src 169.254.63.21
    169.254.0.0/16 dev eth3 src 169.254.119.110

    I am seeing the same behavior when I try to direct connect a Windows laptop to one of these hosts. I can arping the laptop from the Linux host, but ping fails.

    I have some additional information about eth0 on my Linux host.

    # ip link list
    eth0: <BROADCAST, MULTICAST, UP, 10000> mtu 1500 qdisc pfifo_fast qlen 1000 link/ether cc:52af:ea:7d:e0 brd ff:ff:ff:ff:ff:ff

    # ip address show
    eth0: <BROADCAST, MULTICAST, UP, 10020> mtu 1500 qdisc pfifo_fast qlen 1000 link/ether cc:52af:ea:7d:e0 brd ff:ff:ff:ff:ff:ff
    inet 169.254.184.195/16 brd 169.254.255.255 scope global eth0

    #arp -a
    ?(169.254.27.12) at 00:26:9e:cf:09:ce
    [ether] on eth0
    ?(169.254.27.12) at <incomplete> on eth3

    I have discovered that if I down (ifconfig ethX down) eth1, eth2, and eth3, I'm able to ping just fine. What I don't understand is why I can't do this when all the interfaces are up. I guess ping is getting confused when it sees four interfaces all with the same network address. I was nonetheless expecting that if I did a ping -I eth0, that it would avoid any confusion over which interface to send the ping request over.
    Last edited by McGoo; 12-07-2011 at 05:51 PM. Reason: new info

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