Extend VLAN over cable (trunk)


I have 2 BT HomeHub 5, flashed with the latest version of OpenWRT. Each router has 5 ports, Port 1-4 are labeled LAN and port 5 is labeled WAN.

This is what I would like to do:
Router 1 hosts the network, including WiFi and Internet connection. It has multiple VLANs configured onto it.

Since I'm running out of ports, I would like to connect the second BT HomeHub via lan cable and I would like to assign each of the ports of Router 2 to a separate VLAN.

Router 1 switch is configured as follow:

Port 1-4 are part of the VLAN 1 (local LAN)
Port 5 (labeled WAN) is the one I would like to use to connect to Router 2 (I'm assuming that's called trunk).

What should be the configuration on Router 1 and Router 2 so I can assign some ports of Router 2 to VLAN 2 and VLAN 3?


Set up the other router the same way with the same VLAN numbers and all VLANs tagged to the trunk cable port and the CPU. Configure a network interface for each VLAN you want the CPU to be able to use (e.g. to bridge to a wifi AP). If you are only switching a VLAN between Ethernet cables you do not need to send that VLAN to the CPU or have a software network for it.

To pull out one VLAN and send that network out to a regular device, select its port untagged in the VLAN you want and off in all the others. This will work on either router.

Do I have to setup the network interfaces on both? So far I've setup the interfaces only on Router 1. Each interface is using one of the VLANs (eth0.1 for LAN, eth0.2 assigned to GUEST_VLAN, eth0.3 assigned to IOT_VLAN).

I agree with @mk24, but ask myself how Router 1 is connected to the internet, if the WAN-IF extends your VLANs?

Router 1 is connected via VDSL (which is another port of the router, PTSN cable). So the WAN LAN port is actually free.

OK, I see.

That is not necessary. But you should have at least one network IF on Router 2 for management purposes.

That works, thank you!

For future reference, Router 2 should be prepared following: https://openwrt.org/docs/guide-user/network/wifi/dumbap

Also, for a strange reason, both the routers had the same MAC address (c8:91:f9:45:43:e0). I'm assuming that's the OpenWRT default. I had to change the MAC address for the lan interface to something else in order to have both routers on the same network.

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