I have a DHCP server serving a number of subnets over a DHCP relay. When it sends out DHCP offers it sets the server identifier (option 54) to its own IP address.
When the clients need to renew they try to unicast to that IP address, which none of them can route to.
How is unicast to the DHCP server supposed to work when a relay is used? Is the expected behavior for the client to fail to renew by unicast during RENEWING state and then to renew by broadcast during the REBINDING state after time T2?
Best Answer
Yes, absolutely.
It's a little odd for the clients to be unable to route unicast to their DHCP server, but it's not at all a problem; they'll just renew later on in their lease lifetime (which gives you a little less leeway for downtime on the DHCP server).