DHCP relay
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Anyone know how this works exactly?
So in my other thread about the Unifi Switch install I'm going through I've discovered that my VLAN traffic is flowing as desired (static IP works, but the laptop isn't getting DHCP).
Does the switch that the client is directly attached to have to support DHCP relay/helper IP in order for a DHCP request to get past a router to the subnet with the DHCP server on it?
https://i.imgur.com/ecLdpEU.png
Does the switch 10.0.1.10 need DHCP Relay/helper IP? Or is the router at 10.0.1.1 having DHCP Relay/helper IP enough?
I'm thinking that the router is the only thing needing DHCP Relay/helper IP because DHCP is a broadcast, and the router interface 10.0.1.1 is on the same broadcast domain as my VLAN 105 traffic, so the router should handle that process, no?
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It should be just the router. I have never set one up this way though, I've always had the DHCP Server on the same subnet.
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The DHCP relay is configured on the router. Your switch works at layer 2 and DHCP requests run at layer 2, but layer 3 devices stop them from leaving the subnet, unless you them them were to send them. You would have to configure DHCP relay to point to 10.0.0.10 and the DHCP server needs a scope for the 10.0.1.X network.
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OK I found my issue.
I have several VLANs but I'm only providing DHCP for two of them, As it turns out, my Cisco 4400 wireless controller was handling the IP Helper -address portion, not my router.
My router didn't have a helper at all.
Once I added the helper IP to the router, all is well, at least on the laptop. Now to test wireless.
