Is there a way to have 2 modems share 1 WAN port?

General
1

I think I know the answer to this, but I thought I would ask it anyway. The area where I have my peplink is inaccessible to run new wires to because of how my house was constructed. All the cat-5 flows to this area as well as the old phone lines and rg-6 cable. I had comcast and AT&T DSL modems in this location. When AT&T made me switch from DSL to fiber, I had to use one of the cat5 lines running to a bedroom as my WAN line for that device because it was impossible to run fiber to where the router is. now I would like to install an existing starlink dish I have that is not being used. starlink recently made it so you can’t turn off your service entirely and not pay anything. The problem is I only have one cat-5 WAN line to work with. It would be great if 2 modems could share 1 WAN line through the use of a switch on both ends or some other device. Any solutions out there for a situation like this?

2

if the switch is a layer 3 device, you can setup 2 vlan wans. we are doing something similar and it works great. I hope this helps.

in order to get 2 vlan wan licenses for your router, you can wither purchase the 2 vlan wan license or if you have primecare, you get one free and will just need to purchase one license.

2 Likes
3

Evan thanks so much. I want to make sure we are talking about the same thing. Here is how I think it will work. Both the Starlink and the AT&T devices would plug into 2 SFP ports on the layer 3 switch, and the Ethernet cable going to one of the WAN ports on the on the Peplink would plug into the console port on the layer 3 switch. Would there be any configuration to do on the layer 3 switch? Once I get the proper license on the Peplink is there any configuration on the Peplink?

Thanks again for your help.

4

You can share one Cat5 run using VLANs—no console ports needed, and the switch doesn’t have to be Layer-3; any managed Layer-2 switch that supports VLAN tagging works. (wasn’t thinking the other day)

1) On the switch

  • Create two VLANs (e.g., VLAN 10 = AT&T, VLAN 20 = Starlink).
  • Set each modem’s switch port to Access/Untagged in its VLAN (port to AT&T = untagged VLAN 10; port to Starlink = untagged VLAN 20).
  • Pick one uplink port and make it a Trunk/Tagged port carrying both VLAN 10 and 20.
  • Run that trunk port over your single Cat5 to the Peplink’s WAN Ethernet port (not the console).

2) On the Peplink

  • Licensing: PrimeCare includes one VLAN WAN. For two providers over one port, add the second VLAN WAN license.

  • Go to Network → WAN and enable/configure:

    • VLAN WAN 1 with VLAN ID 10 (AT&T)
      • It would be under the Physical Interface Settings, set Uplink Interface to WAN and VLAN to 10
    • VLAN WAN 2 (after license) with VLAN ID 20 (Starlink)
      • It would be under the Physical Interface Settings, set Uplink Interface to WAN and VLAN to 20

  • Configure each like a normal WAN (DHCP/static, auth, health checks).

That’s it—both modems stay logically separate but ride the same physical cable into the Peplink as two independent WANs.

Tip: If your switch has SFPs, you can still do this—SFP vs. copper doesn’t matter; it’s the VLAN tagging that counts.

2 Likes
5

Evan thanks again. This is awesome.

6

No problem buddy, I’m glad that my experience could help you!

7

a console port is for programming not ethernet switching

8

Well I finally got around to working on this, and I discovered that the balance one core that I have does not support vlan wan licenses. At least that is what the 5g store is telling me. Does that sound right? It only supports LAN as WAN, which will not help me since I need starlink and fiber to share the same ethernet cable to the peplink. I am wondering if I can put a managed switch at the modem location and then put another managed switch at the peplink location where I can separate them and plug one into the wan port and the other into the lan port i turn into a wan. Any thoughts on this would be appreciated.
Thanks,

9

The Balance One is getting a bit old, a new B One (confusingly similar name, but different thing) might solve most of the problems.

But you can have two drops to the same switch, with different VLANs, then an uplink which has both VLANs. I think I’ve had a configuration like that in the past.