Help with DHCP helper address and NT domain login

[karkclent]

Hi all,

I have 2 remote sites connected by Frame Relay link. 1 site is the main office and has a WinNT PDC, DHCP server, and WINS server. I want to be able to have clients at the remote office use DHCP and NT domain services (browse Net Neighborhood) over the WAN link.

I have set up the "ip helper-address" on the Ethernet interface facing the clients on the remote site. However, when I do 'debug ip packet detail' on the remote router, I see 'encapsulation failed' for UDP port 67 packets going to my DHCP server. I can ping workstations sucessfully in both directions on the WAN link.

Any ideas? Do I need 'ip helper-address' on the main office router as well? Does 'no ip-directed broadcast' command affect this traffic? (it's on my config)

Thanks in advance,
kc

 

[Wizardof999]

I am dealing with Much the same prolbem in a School environment

I do bleive you need IP helper on both ends for the DHCP request to return back to the remote site. Enven if you set it up i not sure it would hurt anything so give it a try

 

[karkclent]

So you are saying I should put the same 'ip helper-address' command (with same IP) on the router that the DHCP server is connected to?

 

[NewbieGirl]

This may help

http://routergod.com/trinity/

Thanks,
Danielle

 

[karkclent]

Thanks NewbieGirl, but I already digested that one. It's one of my top bookmarks!

 

[MelchiorKD]

in either config mode or interface mode (depending on whether or not you want dhcp on particuler segments) you need to add

ip helper-address "ip address"

this is done on the remote site router. the no ip-directed broacast statement shouldn't have an affect, I have seen configs with it in and with it out. ip helper-address command enables BOOTP broadcast forwarding.

 

[karkclent]

OK, I got this info back from Cisco. My ip helper-address definition is fine. Evidently there's a problem with encapsulation for DHCP requests when forwarding it over the Serial Frame link. (That's what I was seeing in my debugs.) For some reason, the packets were not being encapsulated and passed over the frame when you DON'T configure subinterfaces on the Serial interface. The fix was to move my IP address statement and DLCI definition to a Serial subinterface. The hokey thing is all other IP traffic was being routed OK, including my NETBIOS traffic.

Thanks to everyone who replied with assistance!