DHCP deployment with Secondary address.

[starjakelee]

Hi there,

I haver a some problem with a deployment of DHCP.

There is a DHCP server with two address pool.

One is with major network of Client contained, another is with secondary.

As a example, the two address pool is like 172.30.100.x, 172.31.100.x.

And the interface has two ip addresses like 172.30.100.1 and 172.31.100.1.

When the 172.30.100.x disabled or can not be used, the DHCP doesn't work properly.

I want to use the pool about secondary address.

But the router always answer with major network address not secondary.

How can I use the secondary address pool?

[dgahm]

There is no way to make this work as a secondary. Can you just use a bigger subnet instead?

You could set up another broadcast domain/subnet for the second range. If you are using a router and switch that supports VLANs and trunking this should be easy.

[mhussein]

Try enabling ip dhcp smart-relay on the router. This allows the router to forward the secondary address to the dhcp server. The caveat here is that the router will forward the primary first, then if it doesn't see a DHCPOFFER from the server, the router will start forwarding the secondary address.

Reference:

ip dhcp smart-relay

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122tcr/122tip1r/p1ftdhcp.htm#wp1049986

Regards,

Mustafa