Router as VLAN broker bridge on single managed switch?

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QUESTION :

Will the network configuration below work?

[ 8-port Managed Switch ]

  • VLAN_1: Port 1 = Cable Modem
  • VLAN_2: Port 2 = Router WAN
  • VLAN_3: Ports 3-8 = Other

Can the router on VLAN_2 broker between the cable modem on VLAN_1 and other wired devices on VLAN_3?

I have an obihai which connects to a phone line and another cable tv device which brokers cable outlet to the cable modem as well as plugs into an ethernet port on the WRT54GL’s router switch. The phone line and cable outlets are both next to each other. The problem is that the WRT54GL’s signal degrades greatly in that location.

So, currently, I have a WRT54GL doing NAT, DHCP and routing between WAN and the obihai and cable tv device as well as an RT-AC68U wireless router which is connected via a powerline to a central part of the home and configured as a client bridge which all wireless (and other wired) clients connect to.

ANSWER :

This may vary depending on your ISP, but generally it will work if you do the following.

The cable modem’s Ethernet interface and the router’s WAN or external interface need to be able to communicate. So both Port 1 and Port 2 should be in the same VLAN.

Now if you can connect one of your router’s LAN or internal interfaces to the switch in a separate VLAN shared with the other devices, then things should work fine.

However based on your description, it almost sounds like you want your wireless separate from everything else that is connected and are planning to use a powerline bridge. This will be difficult if you need two network connections between your modem/switch and router. So what you may want to do is to look for an access point (or a consumer router that can be configured as an access point) to locate away from the other devices, which will only require one network connection and leave the device performing as your router by the cable modem (with or without the wireless disabled).

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