DHCP HELP

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dhcp confused

After recently rebooting my Cisco switches, my Windows
2000 server has decided to stop giving out IP addresses. I
have several scopes setup to co-inside with my vlans. Can
anyone explain to me why just rebooting my switches would
cause my dhcp server to stop handing out IP addresses.
There is nothing wrong with the Cisco switches, I have
spent 2 days verifying this. Any ideas would be
appreciated.

Thank You
 
It sounds like you were using ip-helper, DHCP relay, RFC1452 or BOOTP relay
to relay the broadcasts on the VLANs to your DHCP server. Routers don't
propogate broadcasts (and your switch has a layer 3 routing module built
in), so something is needed to get the packets to the DHCP server. Along
the way, the packets get modified so that the DHCP server knows which subnet
the PC should be on.

It sounds as if they'd been configured without writing the config of the
Cisco back to non-volatile RAM. So, when your switch was rebooted, it went
back to the last-saved config.

You need to use "conf t" and add ip-helper addresses and then save the
config back to non-volatile RAM. I'm no Cisco guru, so I can't help with
the specifics.

Hope this helps

Oli
 
Thanks for the response. Yes I am using the IP-helper
command, but it is still in tact. In fact, if we change
the ip-helper to point to another dhcp server, we get an
ip address just fine. This is what I thought as well when
I first started troubleshooting. Is it possible that the
dhcp scopes on the server themselves could have become
corrupt? I spent 2 days with Cisco consultants to help me
verify that the switches were ok. Now I am going to bring
in a Microsoft consultant, because I believe that there is
something wrong with the DHCP service on the server it's
self. Any other ideas are still appreciated. Thank you
again.
 
Hello All,

I do have a few questions if you don't mind.

Is this a AD domain to where the DHCP server is authorized?
If so, does the DHCP logs show any rogue DHCP servers?
Do you have any superscopes created on the DHCP server?
Have you taken a trace on DHCP server to see if the failed requests are
even making it to the server?

Tshooting steps.
********************
When a client fails upon a renewal, start a trace on the DHCP server and
see if any DHCP packets are even making it that far. Chances are, they are
not. Most likely you have the DHCP helper running on the CISCO devices. The
DHCP logs should show this as a rogue DHCP server. Also take a trace on the
client side and see what is coming back to the client as a DHCP server.


Shane Brasher
MCSE (2003,2000,NT),MCSA Security, N+, A+
Microsoft Technical Support

This posting is provided "AS IS" with no warranties, and confers no rights.
 
Hello,

Let's focus on the server itself.

Are you implementing superscopes on the DHCP server?
Are there any event ID's?
How many IP addresses and NIC cards are on the server?
If you look through the DHCP server logs, do you see any event ID's over
50+, if so please copy and paste them on the reply thread.
What do your clients get for an IP address when you have this problem? All
0.0.0.0? An APIPA address? Anything at all? and if they do get an IP
address, if they ipconfig /all what shows up as the DHPC server's ip
address?

Shane Brasher
MCSE (2003,2000,NT),MCSA Security, N+, A+
Microsoft Technical Support

This posting is provided "AS IS" with no warranties, and confers no rights.
 
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