DHCP Server

[hs08]

Hello

Now i have only one router with DHCP server configured in this router. I have plan to make the router redundant using HSRP. So when we using HSRP, should we configure DHCP on both router? If yes, is there any potential ip conflict?

[David Ruess]

Hello,

I believe there are 2 ways you can achieve this that I know of. 

1. Configure half of the IP addresses in the pool on one router and half on the other. There are lots of problems with this design as only the active router can hand out addresses and you can only use half the addresses at a time.

2. Use HSRP aware DHCP. I've only used this with a DHCP server, not on the router but may still work if configured directly on the device. Basically you link the DHCP and the HSRP process together and only the active router hands out IPs but the standby router is also tracking so it can resume IP handout if the active router fails. 

Sample:

https://journey2theccie.wordpress.com/2020/07/20/hsrp-aware-dhcp-relay/

CISCO doc:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp/command/iap-cr-book/iap-i1.html#wp1413119578

Hope that helps

-David

[MHM Cisco World · Accepted solution]

I prefer if you have other L3 device config it as DHCP and config both HSRP router with IP helper toward this L3 device. 
this need HSRP DHCP aware.