Linksys rv016 replying with bot LAN and WAN MAC to arp requests

Discussion in 'Networking Issues' started by MightyDevil, Sep 23, 2008.

  1. MightyDevil

    MightyDevil Addicted to LI Member


    I have a linksys rv016 as a default gateway between our lan and the internet.
    Firmware is 2.0.18.

    Recently some clients on our lan started having intermittent problems accessing the internet. After a bit of searching the obvious we got to the more tricky stuff and found out that for an ARP request, the router would reply with the MAC addresses for its LAN AND WAN port instead of just replying with the MAC for the LAN port. In effect, clients were intermittently pushed the WAN mac address effectively preventing them to get out to the internet.

    The DHCP server provides the right IP for the default gateway at all time.
    To temporarly fix the problem, we've modified the domain login script to include a static arp entry to the LAN port of the default gateway.

    This problem started occuring after upgrading all the workstations to XP SP3, Office 2003, office 2003 SP3, windows updates, avg 8.0. It seems unlikely that the installation of one of the above caused the problem.

    However, at the same time, we also replace our Alcatel speedtouchhome DSL modem with a new Speadstream/Router/Wireless/DSL modem. This new modem is currently hook up to WAN1 on our linksys and we had to input a LAN ip into it as well. We are in the range.

    Why is my linksys broadcasting it's lan AND wan mac address to the clients?
  2. mstombs

    mstombs Network Guru Member

    Sounds familiar to the "hidden" arp problem in Linux many years ago, there was a disputed patch generated to fix it by marking interfaces as hidden.

    I suggest its due to your modem IP range though, does it overlap with the LAN range?
  3. MightyDevil

    MightyDevil Addicted to LI Member

    Indeed you have good flair my friend...the modem HAD a LAN IP in the same range as our LAN...changed it but, it didn't work.

    I think the exact term for this issue, from what I found, is ARP FLUX.

    Changing the IP on the LAN side of the modem didn't help but, removing the patch cord from the LAN side of the modem to the LAN side of our router/default gateway fixed it. Duh!

    It was creating somekind of layer 3 loop or ARP flux I guess. The modem was connected to the WAN side of our router but, since the modem is also a router the thought process of the user who installed it was that we needed a link to it in order to access its config web page...

    Problem solved! Thx :)
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