Resilient DHCP serving

[davehartburn]

It is possible to use a pair of Cisco routers as a resilient DHCP server pair, both using the same address pool?

We are looking at setting a couple up as a HSRP pair, and it would be useful if they could both offer DHCP leases. The most ideal scenario would be a situation where they are aware of which leases the other has offered and not offer those ones.

The research I have done suggests the Cisco DHCP is very much a stand alone unit. Does anyone know any different?

[AxiomConsulting]

Just as a thought, you could add the same DHCP pool to both routers, and by using the 'ip dhcp excluded-address ' place half a pool on one router and the other half on the other router.....

HTH

[davehartburn]

That is an option, or some people split it 80/20. The issue is you need to make sure both routers have sufficient space for your whole address space, to cover a long outage. This means you use twice as many IP addresses.

You can do a DHCP cluster with UNIX or Windows servers, though it would be cheaper and easier if we could do it with the hardware we already have.

[Giuseppe Larosa]

Hello Dave,

we have used this kind of setup for some temporary remote sites.

A feature that can help is the configuration of a DHCP database agent that work as a file repository for DHCP bindings.

see

http://www.cisco.com/en/US/docs/ios/ipaddr/configuration/guide/iad_dhcp_svr_cfg_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1141816

in this case if a router should fail the other one can learn the bindings created by the failed node.

We haven't tried up to now but it looks like interesting.

Hope to help

Giuseppe

[davehartburn]

That does look like what I want. Many thanks for your help.

[gnijs]

Guiseppe,

"in this case if a router should fail the other one can learn the bindings created by the failed node."

I am not sure about this. What are you trying to do ? Let both routers write to the same file and have the databases "merged" ? I doubt this will work (although the tought is appealing, interesting lab exercise :-)