Modem in bridge mode and port forwarding

[Spartan01]

Hi,

I have an XB6 modem in bridge mode with 2 external IPs and 2 Asus routers, each has 1 IP. I port forwarded on first router with no issues, but I need the same port forwarded on the second router. Obviously it should work having 2 separate external IPs. The issue I’m having here is none of the ports can be forwarded at all on router #2. Could be that modem being in bridge mode falls under double NAT or something?
What’s going on, any suggestions?

[mdk]

@Spartan01 --  Could be that modem being in bridge mode falls under double NAT ??

A "bridged" cable-modem does not do any NAT (Network Address Translation) -- it becomes just a "hub" device to "pass-through" the two "public" Shaw IP-addresses to your two routers. 

or something?

You should be able to access the web-interface on "router #2" to configure that router to port-forward. Is this not working for you?

It should: Shaw infrastructure -> Shaw modem/bridge -> Ethernet port #2 -> Router #2 -> your computer -> Router #2's internal web-interface.

Disconnect the power from the Shaw device, wait a minute, and reconnect the power, to "reset" it. Each of your routers should then receive a "public" IP-address from Shaw's DHCP-server.

If you previously have connected a computer to the Shaw device, it will have "consumed" one of your two IP-addresses, and the Shaw device "knows" this fact.  So, the power-off/power-on resets the device, to allow each of your routers to consume your two allowed IP-addresses.

[Spartan01]

Thanks for replying. I’m getting 2 IPs off the the XB6 just fine. My problem is, the second modem can’t do port forwarding for some reason. When I check if that port is open, it is not. I checked 2 different routers as “router #2”. (Every time power cycled the modem obviously in order to assign an IP.)

Gotta be something with XB6 assigning the second IP I guess. They’re both assigned through “one pipe” and might limit some features for second IP?

[rstra]

@Spartan01 

Will the router port forward if it is connected alone?

[Spartan01]

No. I just tried that. The thing is, even if it’s alone it get the same IP assigned as being both connected since the modem binded the MAC address of router#2. 

Another thing I noticed, if I connect another router instead as router#2 it gets a totally different IP than previous router connected as router#2. Is this normal?

[rstra]

@Spartan01 

Yes that is normal to get a different IP because it has a different MAC address. I wonder if you need to add a switch, so modem > switch > routers. I would think it would work the way it was setup.

[Spartan01]

You mean, combine both IP addresses through a switch and then each router connected to that switch?

[rstra]

@Spartan01 

Ya, kind of a long shot, but that is how we connected legacy modems that had more than one ip and had just one port. If you have access to a switch I would give it a try. 

[Spartan01]

You probably mean a managed switch that can handle multiple public ip addresses. 
I just ordered a multiple WAN port router in order to handle both IPs and connect 2 switches to it. I can configure that router to give separate private IPs to each switch. That’s my plan, I hope it’ll work. I’ll let you know. 

[mdk]

@Spartan01 -- Will the router port forward if it is connected alone?

Try this:

1. disconnect both routers from the cable-modem
2. power-off the cable-modem
3. connect that "third" router to the cable-modem
4. power-on the Shaw cable-modem
5. you should get a new-to-you "public" IP-address for the WAN port on that "third" router
6. write-down that public IP-address
7. connect your computer to a LAN port on that "third" router
8. configure that computer's built-in firewall to "allow" traffic to a specific port-number
9. logon to the "third" router's web-server
10. add some port-forwarding definitions for that specific port-number
11. connect some WiFi-enabled computer to any "public" WiFi (Starbucks, Tim Hortons, A&W) and "test" to  try to connect to the port you forwarded on that IP-address that you wrote down, to show that your computer (from #7 above) can receive the forwarded packets

Results? 

Repeat all the above steps, but use your "second" router, not your "third" router.   Results?