DHCP corruption problem, need serious help

S

Shadowspawn

[H]ard|Gawd
Joined
Sep 17, 2002
Messages
1,870
Calling all network administrators; I've got an issue that is driving me up the wall.

I have just completed standing up an AN-30 LOS shot to a remote building. Each end has a Cisco 2851 router and I have built a GRE tunnel between the two as part of the security. Naturally there are other parts to this network but I am most concerned with the tunnel as I believe it is the source of the isse.

The link is active and appears to be fully capable of passing traffic however the DHCP requests coming from the two VLANs on the distant end appear to be corrupted when passing through the tunnel. I am running Netflow Scrutinizer on the distant end of the link and can see the the requests coming from the VLAN gateways and I can see the replies coming from the DHCP server however none of the phones/computers receive IPs and the DHCP server never shows the leases.

I know the issue is not a routing problem as pings to the server sourced from the VLAN gateways work perfectly as well as my ability to SSH into the remote router and switch.

During testing the DHCP server displayed two entries that appeared to be corrupt: mishapen MAC addresses and system names.

I have not added any statements to the tunnel other than the bandwidth (2048). If anybody out there has had experience with this sort of issue I would appreciate the input. This problem is going to drive me nuts and the customer has been waiting too long already.

Thanks,
Brian
 
Any chance of a sh run from the routers? You have ip-helpers? It sounds like you do but want to make sure.
 
Yeah, helpers on the VLANs. I think the server is receiving the request but the rest of the process is failing.

I'm limited in what I can show because of security but I will throw up some basic port configurations in the morning. I am off shift at the moment. I just figured out where the problem was occurring at the end of the shift.

I was hoping someone has experience with this specific issue.
 
The configuration should be nothing more than posting helper-addys to your DHCP servers. Thats all. I have done this with many customers and with my configuration at home. Is your DHCP server on the router or is it dedicated? If its local debug ip packet with an ACL referencing DHCP and include the dump option(hidden to parser).

Also, what do these corrupt MAC addresses look like? You should really post your configuration for some real help.
 
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