arp who-has problem - Debian

This is a discussion on arp who-has problem - Debian ; Hi, i dont know why bud my debian router dont reply on arp requests... have you any Idea what is wrong? Situation: # ip addr show dev eth1 3: eth1: mtu 1500 qdisc htb qlen 1000 link/ether 00:50:8b:60:77:ed brd ff:ff:ff:ff:ff:ff ...

+ Reply to Thread
Results 1 to 2 of 2

Thread: arp who-has problem

  1. arp who-has problem

    Hi, i dont know why bud my debian router dont reply on arp requests...
    have you any Idea what is wrong?
    Situation:

    # ip addr show dev eth1
    3: eth1: mtu 1500 qdisc htb qlen 1000
    link/ether 00:50:8b:60:77:ed brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/24 brd 192.168.1.255 scope global eth1
    inet 172.17.178.1/24 brd 172.17.178.255 scope global eth1:1
    inet6 fe80::250:8bff:fe60:77ed/64 scope link
    valid_lft forever preferred_lft forever

    # tcpdump -i eth1 -n net 192.168.1.0/24
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
    20:36:55.378542 arp who-has 192.168.1.1 (00:50:8b:60:77:ed) tell
    192.168.1.169
    20:36:55.378828 arp reply 192.168.1.1 is-at 00:50:8b:60:77:ed

    # tcpdump -i eth1 -n net 172.17.178.0/24
    tcpdump: verbose output suppressed, use -v or -vv for full protocol
    decode
    listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
    20:34:06.854972 arp who-has 172.17.178.1 tell 172.17.178.12
    20:34:07.854536 arp who-has 172.17.178.1 tell 172.17.178.12
    20:34:08.859466 arp who-has 172.17.178.1 tell 172.17.178.12
    20:34:09.855324 arp who-has 172.17.178.1 tell 172.17.178.12
    20:34:10.854781 arp who-has 172.17.178.1 tell 172.17.178.12

    First IP is well replied, second never.
    Thanks for any help.

    Tomfi


    --
    To UNSUBSCRIBE, email to debian-isp-REQUEST@lists.debian.org
    with a subject of "unsubscribe". Trouble? Contact listmaster@lists.debian.org

  2. Re: arp who-has problem[solved]


    tomfi napsal(a):
    > Hi, i dont know why bud my debian router dont reply on arp requests...
    > have you any Idea what is wrong?
    > Situation:
    >
    > # ip addr show dev eth1
    > 3: eth1: mtu 1500 qdisc htb qlen 1000
    > link/ether 00:50:8b:60:77:ed brd ff:ff:ff:ff:ff:ff
    > inet 192.168.1.1/24 brd 192.168.1.255 scope global eth1
    > inet 172.17.178.1/24 brd 172.17.178.255 scope global eth1:1
    > inet6 fe80::250:8bff:fe60:77ed/64 scope link
    > valid_lft forever preferred_lft forever
    >
    > # tcpdump -i eth1 -n net 192.168.1.0/24
    > tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    > listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
    > 20:36:55.378542 arp who-has 192.168.1.1 (00:50:8b:60:77:ed) tell
    > 192.168.1.169
    > 20:36:55.378828 arp reply 192.168.1.1 is-at 00:50:8b:60:77:ed
    >
    > # tcpdump -i eth1 -n net 172.17.178.0/24
    > tcpdump: verbose output suppressed, use -v or -vv for full protocol
    > decode
    > listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
    > 20:34:06.854972 arp who-has 172.17.178.1 tell 172.17.178.12
    > 20:34:07.854536 arp who-has 172.17.178.1 tell 172.17.178.12
    > 20:34:08.859466 arp who-has 172.17.178.1 tell 172.17.178.12
    > 20:34:09.855324 arp who-has 172.17.178.1 tell 172.17.178.12
    > 20:34:10.854781 arp who-has 172.17.178.1 tell 172.17.178.12
    >
    > First IP is well replied, second never.
    > Thanks for any help.
    >
    > Tomfi
    >
    >


    For archival collection:
    The problem can be very easy investigated via ip route command...
    if there is no route to some network, then router dont respond to arp
    requests from that network.

    decision procedure:
    $ ip route
    172.16.0.0/24 dev eth0 proto kernel scope link src 172.16.0.2
    192.168.1.0/24 dev eth1 proto kernel scope link src 192.168.1.1
    172.17.178.0/24 dev eth1 proto kernel scope link src 172.17.178.1
    default via 172.16.0.1 dev eth0
    #here is everything ok... route to network 172.17.178.0/24 is known.
    #problem was that Iv forgot about policy routing:
    $ ip rule
    0: from all lookup local
    32765: from all lookup main
    32766: from 172.17.178.0/24 lookup 200
    32767: from all lookup default
    #you see that everything from 172.17.178.0/24 goes to table 200
    $ ip route show table 200
    default via 192.168.254.1 dev pobocka1
    #you see missing route to network 172.17.178.0/24 .... so solution is
    #this command: ip route add 172.17.178.0/24 via 172.17.178.1 table 200
    $ ip route show table 200
    172.17.178.0/24 via 172.17.178.1 dev eth1
    default via 192.168.254.1 dev pobocka1


    172.17.178.0/24 via 172.17.178.1 dev eth1 <---------



    Im apologize for stupid question
    Tomfi


    --
    To UNSUBSCRIBE, email to debian-isp-REQUEST@lists.debian.org
    with a subject of "unsubscribe". Trouble? Contact listmaster@lists.debian.org

+ Reply to Thread