DHCP over WAN...questions... 1

[firthm]

Good Morning/Afternoon,

I work for a medium sized organisation with about 200 NT/2000 machines over about 20 sites. Currently they are all static IP and I have been asked to get them to DHCP.

I am familiar with DHCP generally but don't understand a couple of aspects:

*If a node is at a remote site (1 router away from DHCP server) how does the DHCP server know to give that PC a "remote" address (I.e. different to my range at HQ)?

*Do I have to do anything specific with my scopes to set up the above correctly? Whether it be per scope, or globally?

*On a 64k link, would DHCP effect the speed badly (Considering about 6 machines share the link)?

IF anyone can answer any of these questions I would REALLY appreciate it.

Thanks for your help!

Kind Regards,
Mike Firth

 

[ciscoexpert]

DHCP Relay agent - dont know if you have heard about this or not. But the role of the relay agent is to relay the clients request to the server and get the ip address leased to the client.

If for example, there is a Cisco router on your remote site, it can be configured as DHCP relay agent. (IP Helper - thats whats its called in Cisco terminology).

The router forwards all requests from clients on its internal lan (which is enabled with DHCP relay agent) and unicasts or directed broadcast them to the DHCP server. There is a field called GatewayID on the DHCP packet (Check DHCP RFC for any frame format details). This field will be inserted with the IP address of the relay agent. Once the server receives this ip address, it knows from which pool to lease an ip address. The IP address leased would be from the same network as the DHCP relay agent IP address falls into.

Hope that clears your concept on DHCP relay agents.

You can even configure a Microsoft server to act as a DHCP relay agent.

I would say DHCP broadcasts are not gonna hog your bandwidth on the wan link (considering only 6 users)



Sankar Nair
General Datatech l.p.

http://www.generaldatatech.com

 

[firthm]

Sankar,

Thank you very much, this was a very very helpful response, I have awarded you a star for this!

Thanks Again,
Mike Firth

 

[ciscoexpert]

Mike,

Thanks for my 2 cents.

In addition to this, check this FAQ created by RouterGod.

http://www.tek-tips.com/faqs.cfm?spid=557&sfid=988

Sankar Nair
General Datatech l.p.

http://www.generaldatatech.com