DHCP Relay Agent

Do you need a 1542 compliant router for each hop to the DHCP server or just one where the clients are and that will send out a unicast (or directed broadcast is one term I heard) to the dhcp server? I've heard conflicting reports on this. Thanks.

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gojericho0

Just one on the same segment the clients are on. You will put the ip helper command on the Ethernet interface

http://www.cisco.com/univercd/cc/td/doc/product/software/ssr83/rpc_r/48383.htm

rjbarlow

gojericho0 wrote:

Just one on the same segment the clients are on. You will put the ip helper command on the Ethernet interface

http://www.cisco.com/univercd/cc/td/doc/product/software/ssr83/rpc_r/48383.htm

I don't know if it's absolutely so. In the 70-291 MS book II edition ther's an example from which I understood the exact contrary. The image is in the paragraph for DHCP Relay agents.

royal

rjbarlow wrote:

gojericho0 wrote:

Just one on the same segment the clients are on. You will put the ip helper command on the Ethernet interface

http://www.cisco.com/univercd/cc/td/doc/product/software/ssr83/rpc_r/48383.htm

I don't know if it's absolutely so. In the 70-291 MS book II edition ther's an example from which I understood the exact contrary. The image is in the paragraph for DHCP Relay agents.

From what I remember, the books talked about the relay agent being on the segment with the clients. And for routers, they have to be configured with a DHCP IP Helper IP so when they see a broadcast, they know what DHCP Server to relay the request to, gets the response, and relays that information back to the client. Same thing a relay agent would do on RRAS.

dynamik

Yea, this tripped me up a bit on my practice exams. You need to look at it from the right perspective. The way I initially interpreted it was that the relay agent went on the same segment as the DHCP server and relayed information to the other segment. This is incorrect. Relay agents go on the segments that need DHCP but have no DHCP server. You might want to double-check that diagram RJ. I just looked at it, and it looks like this is how they set it up as well.

NetAdmin2436

Yes, from my understanding the DHCP relay agent would be on the 'client' side for normal DHCP requests.

However, when setting up a RRAS VPN server, the DHCP relay agent is actually on the RRAS server. So the relay agent would be in effect on the 'DHCP' side. For example, from my computer at work I VPN to my home server running RRAS and receive an IP address assigned from my Home DHCP server on the VPN connection.

Maybe this is where the conflicting reports came from. Basically the difference between a RRAS VPN server and regular DHCP requests.