Serious help needed!

[MK-2]

OK this is very weird.
We got in today and our Cisco 2600 router was constantly flashing on activity. No network access, and after restarting the switches, router and servers we found that our DHCP and DNS server had gone t*ts up. DHCP and DNS had disappeared off the server. If I go to manage server, its listed as not configured, yet yesterday it was all working.
EMBC say they can ping our router fine, yet internall I get a reply followed by "destination net unreachable"
right now we have the router, one server (now with no dhcp/dns) and my machine with no network access (i can access my machine via remote admin but no http via port 80 normally).
Any help would be VERY much appreciated!

[MK-2]

OK an update:

just checked on the server, at 1:15pm yesterday in event log it shows the DNS server was shutdown (not by us). But now its not even showing as being installed. I think if I can get DHCP/DNS working again (I don't want to just reinstall/reconfigure them without knowing why they disappeared in the first place) then the internet will work again

[Joedetic]

Are the EMBC pinging the WAN side IP Address (IE there side...maybe on a WIC card?) or the internal ethernet port?

Also...if the DHCP has gone t*ts up what default gateway is being asigned?...and that's only if machines are picking up a lease from the server.

Have you tried plugging a laptop directly into these machines via a crossover cable to see if you can get any connectivity using a statically set IP on the laptop?

The dhcp and dns issues....could they be update issues? If you have a linux machine available try nmap <IP ADDRESS OF SERVER> to see what services are running.

I dont know if that helps or not but they are a few things i'd try.

[MK-2]

i have a static ip on my machine, and the gateway is set to the cisco router. but no webpages load. i'm not too concerned about the internet just yet, its more why dhcp/dns just disappeared totally.

it might be an update issue, but things are running so slow right now its taking ages to check anything.
will keep looking, cheers for the help

[Joedetic]

What if you try the opendns DNS servers just to check the internet.

Primary = 208.67.222.222
Secondary = 208.67.220.220

But yes...it does sound a bit suspect. How secure's your admin pass? :P

[sfoord]

Have seem that type of error before.. Normal cause by a fault nic or blown port on switch\Route. When the DNS & DHCP on a windows server gets lots of error it cause them to crash & are unable to restart, until you clear out the DHCP, DNS Databases manual.

First thing you need to know is what is causing the problem.. only way is to check each item in turn with everything else unplugged. i.e. Check server nic with laptop\desktop pc with crossover cable. See if you can talk to each over it. Then when you know the server works ok attach it to the route with nothing else attached and try to talk to it.. Take quite a long time to check though everything, but it the only way

Hope this helps

Ste

[Geoff]

I know it's a bit late now, but you might want to install some monitoring software such as Nagios to help you track down problems faster (it'll even tell you about broken things before anyone realised it's broken).

[MK-2]

Geoff, thanks for the heads up. It's been sorted now, still no idea of a cause but at least we have DHCP and DNS back up. Likely cause was something from Windows update but no proof.

And just to add to matters, we've found that one of our servers has a bad disk in it's array. So there goes another purchase order

I'll look into the software you mentioned for the future, thanks