WAN and LAN in same cable

[Thomas]

Hi SNB's

My first thread here.

I have bridged my old Cisco EPC3925 and is now using an Asus RC-ac87u as DHCP and NAT.
So far so good. Everything worked very fine in the beginning, i.e. when the Asus router were placed next to the cisco router in the basement like this:
CISCO router (bridged) -> Asus router -> LAN.

However, the Asus router needs to be placed on the 1st floor, due to the better wifi coverage and we are going to use the router as a print server.

Right now I am using the typology as shown in the attached image. But when using one of the RF45 outlets, the PC is struggling to maintain a connection to the internet. I am by far no network expert, but my guess is, that the PC is switching between the Asus DHCP server and our ISP's, since the WAN connection is splitted out to all our RJ45 outlets :|

I would appreciate if someone could help me diagnose this problem.

Some solutions I have thought about myself:
1. Using smart switches between the Asus and Cisco router. Then putting the WAN connection on one VLAN and everything else on another VLAN, thus seperating the two networks. Cons is that I have to buy two switches to do that
2. Use the Cisco as DHCP and NAT server and using the Asus as access point. Will this degrade my internet connection in any way? I suppose the NAT handling on the Cisco is 'much' slower than the one on the Asus?

 

[Thomas]

Please excuse my English. It is not my native language.

 

[CaptainSTX]

Please excuse my English. It is not my native language.

Running both the LAN & WAN on a single standard pinned Ethernet cable cable is going to be problematic for the reasons you mention. If you can't run additional cables then you can try splitting the pairs on the existing cable and using two pairs for the WAN and two pairs for the LAN. This will limit your link speed to Fast Ethernet (100 Mbps ) and perhaps less depending on interference.


Until you figure out if you want to add cables or split pairs use the AC 87 as an AP only.

If you want to continue to experiment with your current setup I would suggest that you disconnect the two LAN connections in the basement and instead feed you LAN connection from the AC87.

 

[Thomas]

Running both the LAN & WAN on a single standard pinned Ethernet cable cable is going to be problematic for the reasons you mention. If you can't run additional cables then you can try splitting the pairs on the existing cable and using two pairs for the WAN and two pairs for the LAN. This will limit your link speed to Fast Ethernet (100 Mbps ) and perhaps less depending on interference.


Until you figure out if you want to add cables or split pairs use the AC 87 as an AP only.

If you want to continue to experiment with your current setup I would suggest that you disconnect the two LAN connections in the basement and instead feed you LAN connection from the AC87.

Thank you for your thorough reply.

I didn't think about splitting the cable up in two... Clever. But unfortunately I can't do that, since my ISP provides me with 100Mbps (soon 300 Mpbs). Well I could, but I'd rather come up with another solution. Thanks anyway.

What about the VLAN and smart switch option? If it works the way I think it would, will it introduce more latency to the network?

Hmm I will definitely lose some router features using the AC87 as AP, but the question is. Is the cisco NAT so inferior that I would be better off buying a second AC87 to stay with the cisco in the basement? What I am looking for, is a good stable internet connection with as low latency as possible.

 

[CaptainSTX]

Thank you for your thorough reply.

I didn't think about splitting the cable up in two... Clever. But unfortunately I can't do that, since my ISP provides me with 100Mbps (soon 300 Mpbs). Well I could, but I'd rather come up with another solution. Thanks anyway.

What about the VLAN and smart switch option? If it works the way I think it would, will it introduce more latency to the network?

Hmm I will definitely lose some router features using the AC87 as AP, but the question is. Is the cisco NAT so inferior that I would be better off buying a second AC87 to stay with the cisco in the basement? What I am looking for, is a good stable internet connection with as low latency as possible.

If you want to use the AC87 as a router you can double NAT it behind the Cisco. Plug the cable coming from the basement into the WAN port of the AC87.

The devices hooked to the basement Cisco's LAN ports will be on one subnet the devices connected to the AC87's Ethernet ports or Wifi will be on another. If you need interconnectivity between the two LANs you may need to create some routing rules using iptables, but this will less of a kludge, In my opinion, than trying to run both the WAN and LAN on the same cable.

 

[Thomas]

If you want to use the AC87 as a router you can double NAT it behind the Cisco. Plug the cable coming from the basement into the WAN port of the AC87.

The devices hooked to the basement Cisco's LAN ports will be on one subnet the devices connected to the AC87's Ethernet ports or Wifi will be on another. If you need interconnectivity between the two LANs you may need to create some routing rules using iptables, but this will less of a kludge, In my opinion, than trying to run both the WAN and LAN on the same cable.

Thank you.
I will go with the option of using only the cisco's NAT. I don't necessarily need the Asus NAT features, I just want a response and fast network + internet. And I think introducing two NATs will only introduce more processing?

 

[CaptainSTX]

Thank you.
I will go with the option of using only the cisco's NAT. I don't necessarily need the Asus NAT features, I just want a response and fast network + internet. And I think introducing two NATs will only introduce more processing?

Try double NATing and see what the impact is. I currently run in a double NAT with my IoT on my Internet facing router with my more trusted secure devices on my second router double NATed. There can be issues but the latency doesn't seem to be a significant issue for me.

 

[abailey]

Currently your setup is very unsafe. You have the Cisco in bridge mode going directly into your LAN port on your Asus (Lan and WAN but LAN is a problem). This means your inside LAN is connected directly to the internet with no firewall in between. If you want to use the visitor wifi option on your Asus the it will have to be in router mode and not AP mode. Personally I think your idea of having a couple smart switches and running VLANs is not a bad idea. Even running through two additional switches will add less than 1ms of latency. If your looking for inexpensive switches to run VLANs these are pretty decent:
https://www.amazon.com/dp/B00N0OHEMA/?tag=snbforums-20

Or, as mentioned earlier, you can run double NAT.

 

[Thomas]

Currently your setup is very unsafe. You have the Cisco in bridge mode going directly into your LAN port on your Asus (Lan and WAN but LAN is a problem). This means your inside LAN is connected directly to the internet with no firewall in between. If you want to use the visitor wifi option on your Asus the it will have to be in router mode and not AP mode. Personally I think your idea of having a couple smart switches and running VLANs is not a bad idea. Even running through two additional switches will add less than 1ms of latency. If your looking for inexpensive switches to run VLANs these are pretty decent:
https://www.amazon.com/dp/B00N0OHEMA/?tag=snbforums-20

Or, as mentioned earlier, you can run double NAT.

Thank you. The TP-link looks interesting.

Okay that boils down to these three options:
- Use the original setup with two TP-Links, separating WAN and LAN with VLANs.
- Use the Asus as AP and Cisco as router, thus loosing all the nice Asus NAT features.
- Run double NAT

What I need:
- Low latency and stable connection, even with a lot of device connected to the network (that was why I bought the Asus router, which has much more processing power than the Cisco).

Currently I am using the Cisco as router, which runs fine. I am not sure about the latency etc, when more than one device is using the network though. Will it be worth it loosing some latency introduced by the smart switches, just to be able to use the Asus's NAT? And will that extra latency even out, when more devices are using the internet simultaneously?

EDIT:
Would it be possible to use VLAN with the Asus, so I only have to use one smart switch?

 

[sfx2000]

Just as a side note - google queries are always interesting...

"one-armed router"
"router on a stick"

It's entirely possible to use one physical connection for multiple virtual lans (VLAN)...

 

[Thomas]

Just as a side note - google queries are always interesting...

"one-armed router"
"router on a stick"

It's entirely possible to use one physical connection for multiple virtual lans (VLAN)...

I used much of my evening yesterday searching for 'Router Bridge WAN LAN' and other search terms including 'VLAN', without any luck.
"one-armed router"
"router on a stick"

Just what I needed. Thanks.

 

[sfx2000]

Just what I needed. Thanks.

Best of luck!

Linux networking is very flexible - just keep in mind that a One-Armed router will not have the same total thruput as a device with multiple interfaces...

 

[Thomas]

Best of luck!

Linux networking is very flexible - just keep in mind that a One-Armed router will not have the same total thruput as a device with multiple interfaces...

Yes there must be a penalty of doing so, but question is, how much.
Do you think that the penalty is greater than just using the Cisco's NAT and DHCP and the Asus as AP? Here I assume that the Asus router is faster at NAT'ing than the Cisco.

 

[sfx2000]

Here I assume that the Asus router is faster at NAT'ing than the Cisco.

NAT performance is probably similar between the two - what one loses with the Cisco is flexibility compared to what the Asus can offer...

 

[Thomas]

NAT performance is probably similar between the two - what one loses with the Cisco is flexibility compared to what the Asus can offer...

Yes that's true.
And equally important; it is funny to play with.

 

[kvic]

I don't miss any features in AsusWRT. NAT, routing and latency in particular aren't shining. So I'm biased in that sense.

I would actually turn the Asus into AP and use the CISCO as router. I would avoid complicating the network with two or more smart switches and run VLANs over it. You're splitting one 1Gbps cable between two pipes (WAN and LAN). Essentially only 500Mbps at most in each pipe dependent on usage scenarios..

The cisco shall be sufficient for NAT and routing. If you aren't happy, consider a wire only router to put it behind cisco. Cleaner, cheaper and faster I think.