RT-AC66U B1 - LAN interface acts strangely

[Bill_Stewart]

The Broadcom SoC routers (like the RT-AC66U B1) have what I regard as a rather strange default setup. That is the MAC address of the WAN port is the same as the MAC address of the LAN bridge. I can see why that is (all ports are physically part of the same switch chip) but it's "just wrong" in my eyes. So in your case you are plugging two different interfaces into your gigabit switch that have the same MAC address! By using the MAC Clone option you are making them have different MAC addresses (as it should be IMHO). Anyway, that's my current theory.

Unfortunately, this didn't work. I changed the MAC address for the WAN adapter on the "WAN - Internet Connection" page to a different MAC address, but this had no effect on the problem.

I am thinking the only resolution is to use managed switches instead of unmanaged switches and create a VLAN for the internet traffic.

If I do this, then I would need two managed switches?

 

[noah way]

That won't work because then there's no connection back to the DSL modem. (Remember, there are two interfaces on the router.)

That won’t work because you say it won’t work or because you tried it and it didn’t work?

Somebody correct me if I’m wrong but the WiFi router has input (WAN) and output (LAN). If multiport the LAN also functions as a switch.

 

[Bill_Stewart]

At the bottom of your diagram go from link > switch > router TO link > router > switch

Here's why what you are saying won't work:

As you can see, there's no way for the router to get to the internet this way.

 

[ColinTaylor]

Unfortunately, this didn't work. I changed the MAC address for the WAN adapter on the "WAN - Internet Connection" page to a different MAC address, but this had no effect on the problem.

Oh well, it was worth a shot. Are there any messages in the router's syslog? I'm kind of expecting it to be freaking out.

I am thinking the only resolution is to use managed switches instead of unmanaged switches and create a VLAN for the internet traffic.

If I do this, then I would need two managed switches?

That would seem to be the obvious way to separate the two networks. Yes you'd need two managed switches, but I don't know whether your powerline adapters might be a problem there.

 

[noah way]

Here's why what you are saying won't work:

View attachment 28391

As you can see, there's no way for the router to get to the internet this way.

TP Link > WiFi WAN port / WiFi LAN port > switch

 

[Bill_Stewart]

TP Link > WiFi WAN port / WiFi LAN port > switch

So you mean this:

Now the problem is that the devices on the other end of the other powerline adapters can't access the LAN or the internet.

 

[Bill_Stewart]

Oh well, it was worth a shot. Are there any messages in the router's syslog? I'm kind of expecting it to be freaking out.

That would seem to be the obvious way to separate the two networks. Yes you'd need two managed switches, but I don't know whether your powerline adapters might be a problem there.

The connectivity between devices on a powerline network is basically layer 2 (just like an unmanaged switch). I have a suspicion that if I did this:

...that I would run into the same problem - because we are putting both interfaces of the router on the same network segment. Not sure why this works with the RT-ACRH13.

It seems the following should work and do what I want:

Thoughts?

 

[ColinTaylor]

It seems the following should work and do what I want:

View attachment 28397

Thoughts?

Yes I was thinking of something like that, but I'm not a VLAN expert so I'd wait for someone more knowledgeable to confirm. My concern was whether your powerline adapters would strip off the VLAN ID from the Ethernet frames travelling over them.

 

[Bill_Stewart]

For the benefit of other readers:

It turns out that creating a VLAN for the WAN interface on the router resolves this issue.

Thanks to all who commented and assisted.