In case two DHCP pool confined on both routerA/B.

[syjeon]

Hi

If DHCP pool is configured on both router A/B which is placed in same VLAN for the gateway, how it will work?

For example How Router A offer the IP address a.a.a.a, then, Router B detect a.a.a.a is already offered, and offer another IP c.c.c.c on Router B?

is there any way to check in-between Router A/B to avoid any duplicated IP to assign the IP address? 

we have to configure local DHCP pool for the redundant purpose, in case of Router A is failed, then Router B should offer the IP address instead.

Thanks.

[Mark Malone · Accepted solution]

Hi use an MS server instead , what your trying to there is not recommended by Cisco and will cause issues , routers have basic DHCP services they are not built for redundancy for that service , its something that's come up a few times , you could split the pool either but don't have same pool both devices

https://supportforums.cisco.com/discussion/9914201/same-dhcp-pool-redundant-routers

[ALIAOF_]

What Mark said is right.  I however had a need to do get something like this done.  Had two routers setup with HSRP.  Both had DHCP running but obviously issues with the IP conflicts.  So I disabled the DHCP on the secondary router and created an EEM script that would detect the pattern in the log.  In this case "standby router taking over and becoming active".  And it would run the command to enable the DHCP server.

Similarly, when the router went into standby state command would disable the DHCP server.  Again this is not the best way to do it and it was still annoying :).