Standby DHCP server

[jimmy.joseph]

Can we have two DHCP servers sitting in the same network responding to requests from multiple networks across WAN..

I might be talking stupid..but still would like to know ...I'll makethe scenario more clear..

I have 3 subnets in my branch office. They talk to the DHCP server in my Datacenter across WAN through Ip helper address at router interface.

Now i'm planning to place one more DHCP server in the same datacenter network with the same scopes as the primary one.Is there a way to instruct the router to forward the DHCP request to two destinations in the same network ,so that the second one responds if the firstone is down.

Thanks in advance ,

jimmy.

[svermill]

I wouldn't know anything about how to configure the servers themselves for redundant operation. From a helper address perspective, you can add multiple unicast addresses or you can define the helper as the broadcast address for the subnet on which the servers reside.

[jason.griffin]

Just add the other ip helper. the IOS looks at the ip helpers in the order they are listed in the running config. if the first does not reaspond it will go the the second

[svermill]

Are you certain of that? I was under the impression that the IOS forwards the request to all listed helpers every single time. How does it know if the server responds or not?

This is a trivial matter unless there is some requirement for one particular server to be "primary" and the other "secondary." I would think this might be the case if they are both dipping into the same pool. There must be a need to syncronize the servers so they don't both dish out the same address. Right?

[jason.griffin]

You are correct. the IOS forwards the request to all listed helpers. I dont know what I was thinking.

The first server to respond with a vaild ip address will fill the DHCP request.

[syed_link]

The question which you had arised is posible but your network will be slow. Because usully DHCP uses the method of broadcasting.