Will a slow modem bottleneck LAN-to-LAN connections via an access-point/switch?

Sykaas · December 2, 2019

I have a non-wireless modem-router (Ovislink OV604V) with some devices plugged into the LAN ports there. From one of those LAN ports, I have an ethernet cable running across my home, connected to the LAN port on a router in another room. This router acts as the wireless access point, as well as having my PC and consoles plugged into it. It acts as a network switch. The modem is doing the routing and DHCP.

I'm looking at upgrading my router because it's quite old and doesn't do 5GHz wifi (it also cuts out sometimes). I have my eye on a gigabit router. I understand that this won't upgrade my internet connection, but since the router isn't actually doing the routing and is only an access point/switch for my modem network, will two devices, both plugged into the gigabit router, be able to achieve gigabit speeds between them?

Example 1: If my PC is plugged into the gigabit router, and a NAS is plugged into that same router, would a file transfer between the NAS and the PC be able to achieve the full potential speed, or would it be "passed through" the (aging) modem and be bottlenecked?
Examople 2: Would connecting my phone to the 5GHz network on the router allow it to get a fast connection from Steam link on my PC, without a bottleneck from the router?

The router I'm looking at is D-Link DIR-867. I won't be upgrading the modem soon because my apartment building is going through the process of having fibre installed so I'm waiting until that goes through before modem shopping or upgrading my service.

Oshino Shinobu · December 2, 2019

It will just go over the router the two are connected to, it won't go to the modem/router.

Local traffic mostly goes over Layer 2 communication, which uses MAC/Physical addresses, not IP addresses. As the router (or really, the switch part of the router) knows where the devices are located by their MAC address, there's no reason to forward anything to the gateway (your modem/router).

Sykaas · December 2, 2019

Thanks, that makes sense.

mtz_federico · December 2, 2019

8 hours ago, Sykaas said:

The router I'm looking at is D-Link DIR-867.

I have not had a good experience with d-link routers, I haven't used that model. I would recommend Netgear or asus (just don't buy their "Gaming Routers", Its just a waste of money)

Sykaas · December 15, 2019

On 12/2/2019 at 6:19 AM, mtz_federico said:

I have not had a good experience with d-link routers, I haven't used that model. I would recommend Netgear or asus (just don't buy their "Gaming Routers", Its just a waste of money)

I bought it for 40% off and I'm very happy with it.

Kisai · December 16, 2019

On 12/1/2019 at 9:57 PM, Sykaas said:

I have a non-wireless modem-router (Ovislink OV604V) with some devices plugged into the LAN ports there. From one of those LAN ports, I have an ethernet cable running across my home, connected to the LAN port on a router in another room. This router acts as the wireless access point, as well as having my PC and consoles plugged into it. It acts as a network switch. The modem is doing the routing and DHCP.

I'm looking at upgrading my router because it's quite old and doesn't do 5GHz wifi (it also cuts out sometimes). I have my eye on a gigabit router. I understand that this won't upgrade my internet connection, but since the router isn't actually doing the routing and is only an access point/switch for my modem network, will two devices, both plugged into the gigabit router, be able to achieve gigabit speeds between them?

Example 1: If my PC is plugged into the gigabit router, and a NAS is plugged into that same router, would a file transfer between the NAS and the PC be able to achieve the full potential speed, or would it be "passed through" the (aging) modem and be bottlenecked?
Examople 2: Would connecting my phone to the 5GHz network on the router allow it to get a fast connection from Steam link on my PC, without a bottleneck from the router?

The router I'm looking at is D-Link DIR-867. I won't be upgrading the modem soon because my apartment building is going through the process of having fibre installed so I'm waiting until that goes through before modem shopping or upgrading my service.

The correct installation is to have the device acting as the modem or fiber router do the DHCP dispatching, and all other devices that are capable of acting like a switch or access point connected to the LAN ports on this device, and turning off any DHCP support on those other devices. Or if you can not do this, set the DHCP subnet to different ones. eg 192.168.0.1 mask 255.255.255.0 for the subnet with the modem and 192.168.1.1 mask 255.255.255.0 but then devices on separate subnets won't talk to each other.

My preference is to avoid NAT-behind-NAT solutions and if you want to prevent certain kind of activities, actually dump all your not-so-smart devices like SmartTV's behind one subnet, and only have the game consoles and PC's on the modem's subnet. That way those smart devices are less likely to be hacked by something malicious running on the PC's subnet. But you also lose some functionality that way (eg chromecast's won't work this way.)

If you are security minded, you'd actually turn the DHCP off entirely and manually assign IP addresses to all devices you are aware of, however this is so much more of a pain in the butt than it's worth. So assign all your fixed assets a fixed IP address in the DHCP pool by MAC address so that you can give them forwarded ports if something calls for it, and let wireless devices come from the dynamic pool.

Sykaas · January 1, 2020

On 12/15/2019 at 9:22 PM, Kisai said:

The correct installation is to have the device acting as the modem or fiber router do the DHCP dispatching, and all other devices that are capable of acting like a switch or access point connected to the LAN ports on this device, and turning off any DHCP support on those other devices. Or if you can not do this, set the DHCP subnet to different ones. eg 192.168.0.1 mask 255.255.255.0 for the subnet with the modem and 192.168.1.1 mask 255.255.255.0 but then devices on separate subnets won't talk to each other.

My preference is to avoid NAT-behind-NAT solutions and if you want to prevent certain kind of activities, actually dump all your not-so-smart devices like SmartTV's behind one subnet, and only have the game consoles and PC's on the modem's subnet. That way those smart devices are less likely to be hacked by something malicious running on the PC's subnet. But you also lose some functionality that way (eg chromecast's won't work this way.)

If you are security minded, you'd actually turn the DHCP off entirely and manually assign IP addresses to all devices you are aware of, however this is so much more of a pain in the butt than it's worth. So assign all your fixed assets a fixed IP address in the DHCP pool by MAC address so that you can give them forwarded ports if something calls for it, and let wireless devices come from the dynamic pool.

I already know all of this, and I already have a single-NAT setup for gaming. I even said in my original post that the modem is doing the DHCP. And I have static IPs on both my pihole and my gaming computer. My question wasn't about how to set up a separate modem and router; I just needed to know whether having a modem and router setup where the modem is slower than the router would affect LAN speeds between two devices connected directly to the router.

And the answer is no, it doesn't bottleneck. I'm able to stream from my PC to my phone at the increased speeds, since those are both connected to the router, not the modem.

As for security, my solution is to not own "smart devices". They're a crock anyway, and even my "Smart TV" isn't connected online. I just need a dumb TV since my PC is hooked directly to it anyway.