dhcp relay agent not relaying

**dales** · #1 16-Aug-2008, 10:05 PM

Hi all,

I'm afraid its another numpty moment as im sure there is something simple im not doing. My set up is as per the diagrams below. I've got one domain and a child domain, the parent dc hosts dns and dhcp on switch one and the child domain is connected to both switch one and two by seperate network cards.

parent domain is configured for 192.168.1.x and child card 2 on child domain is set up for 172.16.10.x.

On the DHCP server I have configured both scopes.
Now onto the child dc I have configured the dhcp relay agent. Firstly I configured it on the 2nd network card (172.16.10.x) only as this does not have a direct link to a dhcp from that switch but after that didnt seem to work I configured it on both to see what would happen still nothing. I can see requests being recieved but also some being discarded but no replies are received or discarded.

I can understand why it would do this for 192.168.1.x as that has a perfectly good dhcp server on its side but the 172.16.10.x just doesnt seem to be passing the requests to the other card.

I dont know why this isnt working and its rather annoying because all the books just have a quick little bit of text on it that says enable it and it will work. Would anyone be able to have a quick look at the configurations in the attachments and suggest to me where i'm going wrong.

network diag

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**Bluerinse** · #2 16-Aug-2008, 11:47 PM

Well my guess is that because you have two NICs in your Exchange box on different subnets, you need to set up *routing* in Routing and Remote Access, on that box.

Check this out..

http://www.computerperformance.co.uk/Litmus/rras.htm

**dales** · #3 18-Aug-2008, 10:01 AM

thanks for that bluerinse, I'll give that a go later and see if that cures it (and have a read of that chapter at lunch time). So if I set the 2nd nic's ip address to within the 192.168.1.x range because it was in the same subnet it would pass the relay on automagically would it. hmm I'll have a play with that then.

**dales** · #4 19-Sep-2008, 10:05 PM

Sorry to drag an old thread up but I think the main problem was the fact that the rras server at the time was a member server and needed to be added to the RAS and IAS security group. I'm still fiddling with rras but its slowly coming together.

**Sparky** · #5 19-Sep-2008, 10:16 PM

Dunno if this will help mate but on the second NIC I generally dont specify a gateway (just keep it blank) and then RRAS should route traffic as needed.

Can you browse the tinternet from the child domain?

**dales** · #6 20-Sep-2008, 09:25 PM

have not quite finished setting it up yet so not sure, I was fiddling with it a while ago, you know just seeing what would happen without really reading that bit of the books. NOw I've actually read the books I think I've got a decent chance of making it work. I'll give it another try and report back