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WRT54G - Internet unreachable for hosts with static IP

Discussion in 'Cisco/Linksys Wireless Routers' started by dpodd, Jun 25, 2007.

  1. dpodd

    dpodd LI Guru Member

    __ The problem __

    An XP machine assigned a static IP will suddenly lose connection to the internet, but all other machines using DHCP can still connect. The only solution is to soft reboot the router, and then the static IP machine can reach web correctly.

    Recently I configured a second XP machine with a static IP and it exhibited the same problems as the other static IP machine. On the internal LAN the machines were still all reachable and responding correctly.

    Bit torrent (Azureus) will still happily run on the machine with static IP even when 'web' is unreachable. Could this point to a DNS issues? Ie I can't connect to google.com, but can connect to bittorrent peer IP.


    __ The setup __

    Internet ADSL <-> WRT54G <-> hosts

    WRT54G latest linksys firmware

    Hosts: Xbox (DHCP), XP x 2 (DHCP), XP (Static IP, outside DHCP address range)

    XP Static IP machine has Web & FTP server running and WRT54G has port forwarding to allow connections from Internet ADSL -> WRT54G -> XP Static IP. This all works fine.


    __ The solution? __

    Well, I'm hoping some has either heard of this problem or more realistically can help me narrow down what to look at. So far I've found the threads listed below that may be relevant. I think people in these threads may be hitting similar issues to me, but not quite using the correct terminology in their posts.

    WRT54G - Cannot ping internet but still connected
    Resetting a WRT54G many times a day
    WRT54GS Loss Of connection when using Azureus

    I am going to do some tests around DNS. This problem is intermittent (every few days) for me, so the next time it happens I will do nslookup of some site from working DHCP PC and then try and ping the IP address from static IP machine that has lost 'web' connection.

    I do not think it is related to Bittorrent (Azureus) because machines with DHCP assigned addresses can run Azureus without experiencing this issue. However, could it be that there are only so many network connections assigned by WRT54G for a machine with static IP and bittorrent has used them all up?

    Give me any gory details you think appropriate. I'm IP & IT proff

    Cheers
     
  2. slam5

    slam5 LI Guru Member

    You need to add the dns server of your isp so that you static ip xp box. when you disable dhcp on a machine, you also disable its ability to query the dns server.
     
  3. DMcCunney

    DMcCunney LI Guru Member

    One question: why are you configuring an XP machine with a static IP at all? Why not use DHCP throughout?

    At a guess, the Linksys is having issues with the mix of DHCP and static addresses.

    I think Bit Torrent continues to work because you've already established connections with the other peers. Other things like web access don't because you can't establish new connections.
     
  4. frenchy2k1

    frenchy2k1 LI Guru Member

    He is using static IP to run server services. You cannot forward ports on a dynamic IP (as you have no certitude it will always get the same IP).

    You run bittorrent with the default firmware. As you said, the router is configured, by default, to track 2048 connections. The real problem is that it tracks those for 7 days (!). I would recommend switching to a 3rd party firmware. Those allow you to choose those parameters (frequent solutions include to increase the table to 4096 entries and especially to track those only for 10 minutes).
    What version of the WRT54G do you have? Look under the router to the serial number. Depending on version and preference, 3 well developped firmwares are HyperWRT thibor (very close to the linksys interface, but offers more options), DD-WRT and tomato.

    Otherwise, as stated earlier, you should also check your DNS settings (make sure that either your ISP DNS or the router IP at least is as DNS for the static IPs) and your DHCP setting (make sure your static IP is outside the DHCP range.
     
  5. dpodd

    dpodd LI Guru Member

    Thanks for the responses.

    Frenchy, you're correct that I am using a static IP so that I can portforward to a web server on my static IP machine.

    I am leaning towards the max connection limit as being the cause. Based on the 7 days before a connection can be reused it is quite possible that this is the cause. I guess this wouldn't have been an issue in the days before torrents!

    However, I'd still like to rule out DNS causing any problems. My static IP machine has its DNS address set to the default gateway which is the WRT54G (192.168.1.1)

    nslookup from static IP XP,

    C:\ nslookup linksysinfo.org
    DNS request timed out.
    timeout was 2 seconds.
    *** Can't find server name for address 192.168.1.1: Timed out
    *** Default servers are not available
    Server: UnKnown
    Address: 192.168.1.1

    Non-authoritative answer:
    Name: linksysinfo.org
    Address: 216.139.210.45


    The router has my correct ISP DNSs under Status -> Gateway so I assume when the router receives the DNS request it knows that it should forward it to the ISP DNS ..?

    Anyway, unless there is something in that description about my DNS setup that could be causing *long term intermittent* (ie not just a slow response here or there) problems then I think I'll look into a new firmware.
     

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