How do I use the DSL-AC68U as a modem only?

[thewizard1241]

I want to use it as a modem only to connect to another router. How do I achieve this without a double NAT?

My first trick was to simply turn off the wifi on the DSL and connect it to the router, which works fine. But then i heard about double NAT.

Turning off NAT kills the internet connection, so that wont work.

Theres also a bridge mode, should i be using that mode instead? Im not sure how to go about configuring this

Thanks

 

[L&LD]

Use Bridge mode.

 

[thewizard1241]

Use Bridge mode.

Ok thanks, I configured bridge mode solo but dont get any internet connection? I read somewhere bridge mode doesnt support VLAN tagging, which my ISP uses, should i configure the VLAN tagging on the other router?

Cheers

 

[dfunked]

Do you have an ISP provided router? Just thinking it might be worth seeing if you can use that in bridge mode instead.

My DSL-AC68U played havoc with my internet connection in the past (kept getting interleaving forced on for over a year), so I eventually gave up and got a Vigor 130. Expensive solution, but it's absolutely bulletproof!
Probably not a popular opinion, but you're really best of sticking to the BT/OR approved list of modems, which this isn't on.

 

[thewizard1241]

Do you have an ISP provided router? Just thinking it might be worth seeing if you can use that in bridge mode instead.

I do but nope, its locked down tight. My isp doesnt like us using any other router other than theirs unfortunately

 

[CaptainSTX]

My first trick was to simply turn off the wifi on the DSL and connect it to the router, which works fine. But then i heard about double NAT.

What did you hear about a double NAT setup that discouraged you from using it? If it is speed or latency I can send you the result of some testing that I did which showed no measurable impact.

The downside of using a double NAT is it is more difficult to run a server behind the second router. Port forwards require forwarding the ports on both routers.

I have run in a double NAT setup off and on for the past fifteen years with no issues. Most of the negative comments you hear about double NAT and NEVER DOUBLE NAT are from people who have limited experience with that type of setup and pass on the folk lore that a double NAT is to be avoided at all costs.

If you have a purpose for a double NAT then go ahead and do it. If you don't have a need/purpose then keep things simple and skip the double NAT.

 

[thewizard1241]

What did you hear about a double NAT setup that discouraged you from using it? If it is speed or latency I can send you the result of some testing that I did which showed no measurable impact.

The downside of using a double NAT is it is more difficult to run a server behind the second router. Port forwards require forwarding the ports on both routers.

I have run in a double NAT setup off and on for the past fifteen years with no issues. Most of the negative comments you hear about double NAT and NEVER DOUBLE NAT are from people who have limited experience with that type of setup and pass on the folk lore that a double NAT is to be avoided at all costs.

If you have a purpose for a double NAT then go ahead and do it. If you don't have a need/purpose then keep things simple and skip the double NAT.

I heard it causes gaming issues or something like that. I never really had speed or latency in mind but glad to know it shows no impact

Im not interested in running any servers, but lets say i forward ports for a game, so would i simply have to just do the same on the second router?

Im not purposely trying to double nat, im trying to avoid it but if i cant, i just hope it doesnt cause issues.

If i do double nat, what things should i disable on the first router? I was thinking perhaps, DHCP, UPNP, QoS...anything else?

 

[CaptainSTX]

If i do double nat, what things should i disable on the first router? I was thinking perhaps, DHCP, UPNP, QoS...anything else?

You can't double NAT if you disable DHCP on the first router. UPnP should be disabled on all routers as it can be a security risk. Disable QoS and if you don't want to use the WiFi on the first router turn off its radios. As for port forwards see what happens if you do none. If it creates a problem then on the first router forward the port to the LAN IP of the second router. This will be the IP assigned to this router by the DHCP server on the first router. On the second router forward this port to the gaming console.

I am currently in a double NAT setup and don't need to forward any ports but I am not a gamer so your results may vary.

 

[thewizard1241]

You can't double NAT if you disable DHCP on the first router. UPnP should be disabled on all routers as it can be a security risk. Disable QoS and if you don't want to use the WiFi on the first router turn off its radios. As for port forwards see what happens if you do none. If it creates a problem then on the first router forward the port to the LAN IP of the second router. This will be the IP assigned to this router by the DHCP server on the first router. On the second router forward this port to the gaming console.

I am currently in a double NAT setup and don't need to forward any ports but I am not a gamer so your results may vary.

If i disable DHCP on the first router and then provide a static IP to the second router, would that be fine? Ok ill disable upnp and wifi. And ill test out the port forward, maybe i wont have to worry about that but lets see. My second router is actually coming tomorrow so i'll let you know the results!

And thanks for this guide much appreciated!

 

[CaptainSTX]

If i disable DHCP on the first router and then provide a static IP to the second router, would that be fine?

You can do what you suggest BUT the IP you assign must be in the subnet of the first router and will be the WAN IP of the second router. You then must use a different subnet for the LANs subnet on the second router.

The way I usually handle this is set the second router to automatic DHCP and then on the first router give the second router a static/sticky IP outside the DHCP range the first router uses to assign LAN IPs. Again the LAN subnets on each router must be different.

 

[thewizard1241]

You can do what you suggest BUT the IP you assign must be in the subnet of the first router and will be the WAN IP of the second router. You then must use a different subnet for the LANs subnet on the second router.

The way I usually handle this is set the second router to automatic DHCP and then on the first router give the second router a static/sticky IP outside the DHCP range the first router uses to assign LAN IPs. Again the LAN subnets on each router must be different.

The way you handle it is exactly what i had in mind really. So i can give the second router a static IP of 192.168.1.2 through the first router, and then give the second routers lan dhcp address of smth like 192.168.0.1 - 255 etc

That should work right?

 

[thewizard1241]

Hopefully i can avoid the double nat by using bridged mode but lets see