VLAN Trunk WAN and LAN

[liug]

Here is the setup:
- 2.5G managed switch in Room 1. The switch has WAN as vlan tag 100 and LAN as vlan tag 200.
- Asus RT-AX86U PRO is in room 2. There is only one ethernet cable running between the two rooms.

The plan is to make this ethernet connection as "trunked" with both vlan 100 and 200 tags. Since the switch supports 2.5G, it makes sense to use 2.5G port on the Asus router.

Is this a supported setup on Asus using Merlin firmware? Can Asus make use of vlan 100 as WAN and vlan 200 as LAN? The WAN IP will be dynamic from upstream dhcp server. Asus will be the dhcp server and default gateway for the LAN.

 

[bennor]

Is this a supported setup on Asus using Merlin firmware?

The Asus-Merlin 3006.102.x firmware supports VLAN's. But don't know if that VLAN support is extended to the router's WAN port. If you haven't done so already, use the forum search feature to find a few past discussions on using the Asus-Merlin 3006 firmware's VLAN with managed switches. For example...
https://www.snbforums.com/search/1530008/?q=3006+vlan+managed+switch&o=relevance
PS: And an Asus support doc.
[Wireless Router] What is VLAN and how to setup in ASUS Wireless Router?
And another one.
[Wireless Router] What is multi-service WAN and how to use it?

Multi-services WAN allows more than one profiles (VLANs) to go in and out the router’s WAN port, it often be used with IPTV or management switch.

 

[liug]

Yeah, I searched earlier and found [one] but no answer. Most posts are for multiple vlans on LAN side only, not across WAN and LAN.

 

[liug]

I thought about this, and here is an idea that may work but I don't have the spare equipment to test it before changing the live network. It would great if someone who have a test lab and spare asus pro routers to test the idea.

On Asus side:
1. Configure Asus to use 1G WAN and leave the 2.5G for LAN side usage.
2. Go to LAN -> VLAN -> Profile to add VLAN ID 100 for WAN_100
3. Go to LAN -> VLAN -> VLAN to change Port 1 to "Access" mode and WAN_100 VLAN/Profile
4. Use a short CAT cable to connect Port 1 to 1G WAN port.

On Managed switch side:
1. Configure VLAN 100 for WAN and VLAN 200 for LAN
2. Pick a port to trunk to Asus 2.5G port, and configure this switchport as trunk port
3. Configure allowed vlan 100 and native vlan 200 (some switch models call this PVID) on the trunk port.
4. Run a CAT cable from this trunk switchport to Asus 2.5G port

To test, create two ports on the managed switch:
- First access port on vlan 100 to be connected to upstream Internet router or cable modem, to provide DHCP WAN IP to Asus
- Second access port on vlan 200 to be connected to a client laptop, to test the outbound Internet connections.

Traffic flow: client laptop -> switch -> untagged vlan -> Asus 2.5G port -> Asus LAN gateway IP -> Asus 1G WAN -> Asus LAN port 1 -> Asus 2.5G port -> tagged vlan 100 -> managed switch -> upstream router / cable modem