DHCP Scope fails randomly 1

[GeorgeTuk]

Hi guys,

Bit of an odd one, in one of our offices with SBS since last week the DHCP scope has gone offline 3 times, nothing else is affected but obviously people lose connectivity.

Its strange since in about 8 years I have never seen DHCP fail once!

Any ideas?

Thanks

George

 

[GeorgeTuk]

Ok have been looking further into it and it seems there maybe another DHCP server on the network or that IP address is being taken by another device. Is there any way I could find that out?

 

[nicolasvdb]

Just look at your clients from which dhcp server they received an ip address

 

[wahnula]

It should be a simple process to access your switches and/or routers to see if their DHCP is turned on. If the client's IP address is 192.168.0.xxx try pinging 192.168.0.1 or 192.168.0.0 etc. You might need passwords if the devices are so set up. More details about your network topology would be good. Could be one of the switches had a CMOS reset that reset it by default to DHCP host.

This could happen if, say, someone plugged a wireless router into your network and it became the DHCP host. Analyze all hardware in the loop.

Tony

Users helping Users...

 

[ShackDaddy]

If you run ipconfig /all on your clients, you'll be able to tell which server provided them with their address, and that should help you narrow things down.

Dave Shackelford
ThirdTier.net

 

[GeorgeTuk]

OK its all sorted now...our Zywall firewall appeared to turn itself on as a unauthorised DHCP server even though the option was definitely off, apparently they can do this after a power cut/turn off (which somebody must of done but no one knows who!).

Thanks for your help guys.

 

[wahnula]

Glad I could help George, thanks for the star. Even a blind frog catches a fly now & then

Tony

Users helping Users...