Wifi bridge occasionally drops all DNS

Discussion in 'Networking Issues' started by sim0n, Dec 17, 2013.

  1. sim0n

    sim0n Reformed Router Member

    Hey folks. Due to some renovation work moving the house's 'center of communications' around, I have a slightly strange network arrangement, one portion of which is like this

    DSL modem -> WRT54G running Tomato ( ->wifi-> a TPLink router running DDWRT ( -> standard wired ethernet to my main computer ( running Ubuntu

    The DDWRT is set to "Client bridge (Routed)" and the main router at runs the DHCP and all that. is also running dnsmasq so all the computers in the house can receive the names for my fileserver and various raspberry pi's and whatnot.

    My issue is that periodically, my computer on the other side of the bridge loses the ability to lookup DNS. This is mainly annoying as every 5 minutes all web browsing halts for about 20 seconds, after which it comes back to normal. If I do 'dig' in the console it gives me "connection timed out; no servers could be reached", sometimes it hangs for a couple of seconds then gives a successful query, but strangely the query time is still listed as being <10ms.
    I've ruled out it being my computer or network card, as I dug up an 8-port switch and hooked up my laptop (also running ubuntu) to go through the same cable and discovered that the DNS nonresponiveness occurs simultaneously on both.

    Also, its not an issue with dnsmasq, because even if I specify an external DNS server (eg: "
    dig www.google.com @"), the request still times out during the period.

    It's only an issue this side of the bridge. I can be ssh'd into my fileserver (which is connected directly to the WRT54G) from where I can happily make DNS requests all day, even while this machine is getting no response.

    And its only DNS that stops, I can still access my fileserver just fine via the IP during the period of no DNS.

    Anyone have a clue of what I should be looking for?
  2. sim0n

    sim0n Reformed Router Member

    This may be be of help. When it drops, I can't ping (the main router).

    64 bytes from icmp_seq=46 ttl=63 time=1.36 ms
    64 bytes from icmp_seq=47 ttl=63 time=1.32 ms
    From icmp_seq=48 Redirect Host(New nexthop:
    From icmp_seq=48 Redirect HostFrom icmp_seq=49 Redirect Host(New nexthop:
    From icmp_seq=49 Redirect HostFrom icmp_seq=50 Redirect Host(New nexthop:
    From icmp_seq=50 Redirect HostFrom icmp_seq=51 Destination Host Unreachable
    From icmp_seq=54 Destination Host Unreachable
    From icmp_seq=60 Destination Host Unreachable
    Pinging works fine. So I was prepared to blame it on the wireless link itself, but pinging other machines that are on the other side of bridge works fine :confused:
  3. sim0n

    sim0n Reformed Router Member

    I've fixed it. If it ever occurs to anyone else: it was an issue with Tomato's static DHCP not liking the wifi bridge http://www.dd-wrt.com/phpBB2/viewtopic.php?p=727836 . In the static DHCP settings on I deleted the MAC addresses for both the bridge router and my own computer and it seems to be playing well for now.
    Last edited: Dec 19, 2013
  4. Jtemp70

    Jtemp70 New Member Member

    Thank you. I had a very similar issue. My wired clients had a constant dns connection, but the wireless clients would drop as you described. I thought it was an issue the router not liking the incoming ddns service, or I had a bridge configuration issue. Different to your situation, though i used your scenario to find the issue.

    I had already zeroed out the MAC & IPs in the bridge, but zeroing out the 3 static DNS entries the Router's DHCP server was handing out. I had it set to itself (

    Can anyone explain why this appears to work?
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice