DHCP Relay on TL-R605
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This thread has been locked for further replies. You can start a new thread to share your ideas or ask questions.
I recently bought an entire Omada Network including the OC200 hardware controller, the R605 Security Gateway, 3 Jetstream switches and 3 EAP access points.
At the moment I am trying to implement DHCP relay configuration because I have a server running a DHCP service which I need to use for a couple of subnets in my environment.
I am used to add DHCP relay configuration to the vlan interface on my routing device/gateway with for example the 'ip helper' command (on Cisco devices). In my setup, the TL-R605 is the routing device/gateway so I want to apply the DHCP relay configuration on that device. This is the point where I get lost: I do not seem to be able to find this particular setting in the Omada controller.
I can only find DHCP Relay configuration on the switches. But for that to work, I have to activate the vlan interfaces in the switch for those particular vlans and that messes with my design: My switches should function as OSI layer 2 switches, only the router/gateway should handle the OSI layer 3 (and higher) traffic. The only vlan interface my switches need, is there own management interface.
Under 'Settings>Wired Networks>LAN>Edit Network' there is a 'Legal DHCP Servers' option, but this only seems to be a DHCP snooping feature and has no DHCP relay functionality as far as I can tell from the testing I have done.
I am curious how others have handled this and if I am overlooking something in the Omada Controller. Is this option available when deploying the TL-R605 as a standalone? Maybe @Fae can shine some light on this?
I appreciate your help!
Edit: I found a simular thread from a few months ago, but no solution or clarity is provided yet.
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Good News!
I had a remote session with one of the engineers from the support team. After checking my configuration, we found the issue causing this.
The tl;dr:
You need to enable VLAN Interfaces for all your VLANs/Subnets. So in my case, I have a my server/shared services separated from my normal clients and needed a VLAN Interface there as well. After I configured and enabled one, my clients got their lease from my DHCP server, which is connected on a different switch and different VLAN.
So go to devices -> click on your switch -> Config -> VLAN Interface -> Edit -> Enter an IP address or set it to DHCP, configure DHCP Relay address -> Apply and then enable the VLAN Interface
Repeat for all switches/VLANs
The details for those interested:
So in my setup things are splitted up nicely:
- one VLAN for all my normal clients (PCs, mobil clients, etc.)
- one VLAN for Guests
- one VLAN for all shared services/servers
- one VLAN for everything IoT related
- one VLAN for management of Omada devices
In my thinking, the VLAN interface was only needed for the client VLAN, as it would act as another gateway and relay the DHCP messages. I have a ER-605 which I thought was responsible routing between the switches. So the interfaces, it had configured should be enough for inter VLAN routing (which in fact is enough for one direction). But the switches need their L3 interfaces as well.
A working example with my address ranges:
- Client Subnet is 192.168.200.0/24 with VLAN 200
- Server Subnet is 192.168.50.0/24 with VLAN 50
- Interfaces on the ER-605: 192.168.50.1 and 192.168.200.1
- DHCP Server address: 192.168.50.2
Since I have two switches I needed four more addresses to cover all SVIs (need to clear the address of my DHCP so the .2 gets available for the SVI):
- Switch1: 192.168.50.100 and 192.168.200.2
- Switch2: 192.168.50.101 and 192.168.200.3
Example config for Switch 1:
Devices -> Switch 1 -> Config -> VLAN Interface
VLAN 200 (enabled):
- Management VLAN: not enabled
- IP Address Mode: Static
- IP Address: 192.168.200.2/24
- DHCP Mode: DHCP Relay
- Server Address: 192.168.50.2
VLAN 50 (enabled):
- Management VLAN: not enabled
- IP Address Mode: Static
- IP Address: 192.168.50.101/24
- DHCP Mode: None
Repeated that on Switch 2 with the other addresses and my client got his lease from my DHCP.
I hope that this makes sense and that it resolves your issues as well. If you have trouble and I should share more of my configuration let me know.
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Hi @dapL!
Thanks for your elaborate reply. Glad to see there is a solution! Not sure this is the solution I was hoping for. In a way it makes sense to enable the vlan interfaces of all involved vlans for DHCP Relay, because normally you would configure DHCP Relay on your L3 device/router which has those vlan interfaces as well.
That is exactly why I find this implementation very weird and not intuitive. It is nice to be able to use your switch as a L3 switch and having these capabilities, but I think it should be present on the router in the first place.
Now we have to make a lot of configuration on our switches (which we intended to work as L2/access switches) to be able to configure DHCP Relay on them, which should be configurable on the router.
@Fae is the implementation of DHCP Relay on the (TL-R605) router on the roadmap for Omada? If not, I would like to make it a feature request.
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