RV042 "duplicate use detected" DHCP

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by jjbraunius, Oct 22, 2008.

  1. jjbraunius

    jjbraunius Addicted to LI Member

    I am having the following issue - IPSEC VPN into the router on WAN2 from another office, working fine for about two months until now. It is running 2 machines and 2 IP phones and a network printer.
    The local main office RV042 is set as DHCP server as is the router in the other office for that remote office. The two are connected via VPN.
    I am getting "duplicate use detected" errors where one machine already has a DHCP address and another is given that address and I get the error of duplicate IPs.

    I started running Wireshark Protocol Analyzer on a PC in the office to see what comes up this evening.

    I'd appreciate any help on this.
  2. Toxic

    Toxic Administrator Staff Member

    are both your lans on the same IP subnet or different?
  3. jjbraunius

    jjbraunius Addicted to LI Member

    You mean subnet masks or internal IP addresses?
    Both have the same subnet mask, internal addresses are different for each router, one starts with 172..... and the other with 171...
  4. jjbraunius

    jjbraunius Addicted to LI Member

    I also had Netbios Broadcast in the VPN setup on the RV042 and the other router doesn't have that, so I disabled it. I also changed the remote networks subnet mask.

    When I disconnected the remove VPN for a day these issues didn't come up so it has to do with the VPN.
  5. jjbraunius

    jjbraunius Addicted to LI Member

    VPN has been disconnected for a week - not a problem with this but today it came up again so it is not VPN related.

    Any other help where to look? Could it be a hacker doing MAC spoofing?
    Looks like my DHCP overflows and can't dish out more addresses.

    The router is on two WAN's - one DSL and one partial T1. Analyzing the logs I get a lot of traffic that is stopped by the firewall on WAN1.
  6. jjbraunius

    jjbraunius Addicted to LI Member

  7. levelup3

    levelup3 Addicted to LI Member

    is really useful for me, I am glad to read it here.
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