Morning everyone. I'm seeing some weirdness with DHCP Relay. We have a Cisco 4331 router connected to Meraki MS210-48P switches running firmware version 15.18. The 4331 router handles all of the layer 3 functions for the network, and has two subinterfaces configured - one for VLAN 1 (0/0/1.10) and one for VLAN 40 (0/0/1.40). The VLAN 40 subinterface has ip helper-address 10.0.10.7 pointing to the domain controller, which handles DHCP for both subnets.
The problem is clients in VLAN 40 are not getting an IP address.
The screenshot below was captured on the DHCP Servers & ARP page under Switching. It gives me the impression that the DHCP server is offering an IP address to the client, but it appears that the client never receives that offer, and ultimately times-out with a message stating that the DHCP server could not be found.
The 4331 is forwarding the DHCP messages to the server, but the responses are not making it back to the client.
Has anyone experienced this issue? Is Layer 3 Routing required for Meraki switches to properly handle the DHCP relay? (I would think the switches are simply receiving a unicast message destined for the domain controller from the router due to the DHCP relay config and no special configuration would be required on the switches to simply pass the traffic out of the correct port to the domain controller)
Morning ww - we are allowing DHCP servers, though I am not sure why the description for the server has a different name for VLAN 40 considering that it's the same server that is listed for VLAN 1. For some reason, Meraki seems to think that the DHCP server for VLAN 40 is the LAN interface of the 4331 router (the listed MAC is for the Gig 0/0/1 interface on the 4331, but I'm assuming this has something to do with the relay config.)