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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 (192.168.0.1) ->wifi-> a TPLink router running DDWRT (192.168.0.2) -> standard wired ethernet to my main computer (192.168.0.5) running Ubuntu

    The DDWRT is set to "Client bridge (Routed)" and the main router at 192.168.0.1 runs the DHCP and all that.
    192.168.0.1 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 @8.8.4.4"), 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 192.168.0.1 (the main router).

    Code:
    64 bytes from 192.168.0.1: icmp_seq=46 ttl=63 time=1.36 ms
    64 bytes from 192.168.0.1: icmp_seq=47 ttl=63 time=1.32 ms
    From 192.168.0.2: icmp_seq=48 Redirect Host(New nexthop: 192.168.0.1)
    From 192.168.0.2 icmp_seq=48 Redirect HostFrom 192.168.0.2: icmp_seq=49 Redirect Host(New nexthop: 192.168.0.1)
    From 192.168.0.2 icmp_seq=49 Redirect HostFrom 192.168.0.2: icmp_seq=50 Redirect Host(New nexthop: 192.168.0.1)
    From 192.168.0.2 icmp_seq=50 Redirect HostFrom 192.168.0.2 icmp_seq=51 Destination Host Unreachable
    From 192.168.0.2 icmp_seq=54 Destination Host Unreachable
    From 192.168.0.2 icmp_seq=60 Destination Host Unreachable
    
    Pinging 192.168.0.2 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 192.168.0.1 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

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