[nSLUG] Static IP woes

Rowan Townshend rtownshend at emslimited.ca
Tue Sep 20 17:30:04 ADT 2005

Hello all,

  Here's how it was laid out before I started going at it.

Internet--->Eastlink SurfBoard--->Router(Wireless)--->Computers & Server

Internet: Lots of it out there.

Eastlink SurfBoard: Model# SB5100 (the same one I believe for most home 

Router: Linksys 2.4 GHz Wireless G (Model#: WRT54G)
    -Setup to acquire an IP via DHCP from Eastlink
    -Router set to have an static internal IP of it's own (all the 
machines in the office point to it as their default gateway)
    -Router operates a DHCP server to provide for the next point
    -Clients are all setup with unique IPs gained via DHCP but keyed 
into each system so there are no IP conflicts (EG:
    -Router uses "SPI firewall" which came with it I understand either 
as stock or with a firmware upgrade
    -A WEP key is used on the internal wireless network (although the 
server is physically connected to the router with a piece of CAT-5e 
network cable, not sure if       it's the same stuff Eastlink would have 
left behind)

  The server is sitting behind the router, and ports have been forwarded 
to it via the Router web interface (53 for DNS, 80 for Apache, etc...).

  I do have the DNS server going, and have been using it for my own 
computer as the Primary DNS (I'm using WinXP on my desktop).  I tried 
doing some "host"ing, and some digs, and now it seems that the server 
does not wish to reply (I was able to get responses when I did these 
from the server command line (telling it to refer to the internal IP 
previous to today).  I was never able to get any reply other then "Host 
not found" when I tried it by the external dynamic IP.  Beyond simple 
"host domain.com nameserver" and "dig -x domain.com" I do not know many 
other tests that could be preformed DNS wise.

  I have not done anything with the firewalls yet, I have not setup 
anything for IPtables.  I can try taking down the Router firewall 
tomorrow at a time when I can make sure the other computers in the 
office will not be affected (or more accurately, the users).

  When the Static IP info was laid into the Router itself, doing 
ipconfig /all resulted in the expected settings.  Seeing the internal IP 
for the machine, the gateway (router), and the Eastlink DNS servers (I 
presume fed from settings on the router where they are keyed in).  Yet, 
there was no external connection outside the router.

Thanks to everyone for the help thus far, time to go home for the day.
-Rowan Townshend

Donald Teed wrote:

> There are a lot of changes involved in what you are working on.
> Without a picture of how it worked before, it is difficult to pinpoint
> the most likely parts to have broken.
> Connecting to your router's web page should show a status
> page confirming if your static IP is assigned properly.  Make
> sure you don't get the internal LAN IP mixed up with the WAN IP.
> Is there a DHCP server running by default on the router?  That
> can confuse clients if they should be getting their IPs
> assigned from elsewhere.
> Have you started to run your own DNS?
> If so, test connectivity to the outside world by IP numbers first
> to determine if DNS configuation is the real source of the breakdown.
> Depending how you had the router and cable modem set up before,
> the network cable might need to be a cross over cable between
> the eastlink modem and your router box - I usually use whatever cable
> the ISP gave me with the modem.
> Also check your router firewall set up.  If you turn it off briefly 
> and discover
> things work as they should, then that is the culprit.  If the slackware
> box is running iptables, try turning that off briefly as well and see if
> something was badly configured.
> If you don' t run the slackware box in a DMZ, you will need port 
> forwarding
> to allow DNS and other essential traffic to pass in.  Make sure that 
> is set up on the
> router.
> These are just some check list items I would normally go through
> in this situation.  You would know which ones really might apply.
> The clients can tell you alot too.  On the Windows box ifconfig /all
> will show you the DNS, gateway, etc. it picked up.


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