Intermittent network fault ... driving us crazy !!

  • Thread starter Thread starter Jethro
  • Start date Start date
J

Jethro

Hi all,

we're a small company with no dedicated network expertise ... so we
have to try and muddle through.

We have a small (about 10) PC network with a 2 W2K servers, and an NT4
server.

One of the W2K servers is a DHCP server and SQL server combined.
The other is the Exchange server, and has 2 network cards. One seems
to connect to a telco (we are in the UK and it's BT !) for mail
provision. The other seems to be the LAN card. Sitting near this box
is an ADSL modem/router, which provides us with internet access, and a
box marked "RoboFireWall".

In order to access the internet from a client PC, we just run IE.
There is no special proxy setting, "Automatically detect network
settings" is OFF.

The problem ?

Every so often, about 3/4 times a day, the internet dies. Sometimes it
comes back on it's own. Sometimes we unplug the router/firewall,
reboot the 2 card server and hope ...

Stangely enough, when the CLIENT PCs lose internet, most times it is
possible for the 2 card server to access it ... a PING from a client
just returns "Unknown host name".

There is a machine in another room which seems to kill the network
when it's connected ... whether this is connected (no pun) I don't
know ... my intuition is that it's a bit of a red herring ... it might
exacerbate the problem, but it isn't the cause ...

Does anyone have any suggestions as to what to look for ... or any
tools or windows programs we can run to help diagnose the problem ?

Thanks in advance,

Jethro
 
It sounds as though your server is using a different
Internet connection than your LAN. That would explain
why it keeps working when the other boxes fail.

Use the "tracert" command from the servers and
the workstations next time this happens to trace a
complete path to any public IP address. Unlike a
ping, this will show you how far things get before they
fall apart.

My guess is that it will turn out to be at the
ADSL line router, which may not be getting an IP address
from your provider, or which may be having trouble
authenticating if it is PPPoE. If it is on a static IP
then we have to look deeper.

Steve Duff, MCSE
Ergodic Systems, Inc.
 
Ensure you have local DNS server, DHCP settings point to this server, and
DNS Forwarders (ISP's DNS) are enabled. If everything plugged in the router
(this is not quite clear), ensure router's DHCP feature (if any) is
disabled. Reorder multihomed machine's network connections in
NetworkConnections menu Advanced/AdvancedSettings... - LAN at the very top.
 
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