Question Connecting 2.4Ghz Modem to 5GHz Router

Jan 9, 2020
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Hello,

At my home I have a cable modem that has only 2.4 GHz option. I want to have a 5 Ghz connection at my home because my new iphone sucks at 2.4Ghz. I found a router that has dual band option of 2.4 GHz and 5Ghz. If I connect my modem to this router, even though my modem doesn't support 5Ghz, can I still get 5Ghz wifi connection? Do I lose any speed or whatsoever? Thank you.
 
Yeah it'll work. The modem will communicate with the router over ethernet, and the router will provide 5 GHz WiFi. Just plug the router's WAN port into the modem, then plug all of your devices into the router rather than the modem. If the modem has a bridge mode, that will be best (saves you from extra work if you port forward), but it's not absolutely necessary. Probably best to disable the modem's wireless too, so you don't get confused about whether your wireless devices are connected to the router or the modem. All your wireless devices should be connecting to the WiFi on the new router. (Only reason I can think of to keep the modem's WiFi active is if the router's WiFi doesn't support a guess network. You can use the modem's WiFi as a guest network, since devices connected to it will have Internet access, but will not be able to contact devices connected to your router.)

If you forward ports and the modem is not in bridge mode, you'll need to forward the ports on both the modem and router. On the modem, find a setting for DMZ, and set it to the router's WAN IP address. Enabling DMZ tells the modem to forward everything to that IP address, and creates a setup very similar to a bridge. After DMZ is set, you can configure port forwarding on the router as if it were connected directly to the Internet.

There should be no speed loss as the throughput over 5 GHz is slower than over Gigabit Ethernet. All the extra hop will do is add like 1 millisec of latency. The most common reason for speed loss in this type of configuration is if the router's WAN port is not Gigabit. Non-Gigabit Ethernet will cap you at 100 Mbps (12.5 MB/s), which is significantly slower than 802.11ac over 5 GHz (which usually tops out at around 866 Mbps, or about 45-60 MB/s throughput after error correction). So make sure the router has a Gigabit port on the WAN side (also nice to have it on the LAN side).

Beware that some of the older dual band routers (like 7+ years old) could do 2.4 GHz or 5 GHz WiFi, but not at the same time. You had to pick one or the other. The ones which could do both at the same time were labeled "simultaneous dual band." Newer routers should be safe, and all capable of using both bands simultaneously.
 
Last edited:

kanewolf

Titan
Moderator
Hello,

At my home I have a cable modem that has only 2.4 GHz option. I want to have a 5 Ghz connection at my home because my new iphone sucks at 2.4Ghz. I found a router that has dual band option of 2.4 GHz and 5Ghz. If I connect my modem to this router, even though my modem doesn't support 5Ghz, can I still get 5Ghz wifi connection? Do I lose any speed or whatsoever? Thank you.
The simplest way to do this is just to turn OFF the WIFI on your cable modem/router and plug the WAN port of your second router into the LAN port of the cable modem/router. If you don't need special NAT settings that will "just work".
The more advanced method would be to do what @jeremyj_83 suggests. Put the combo unit into bridge mode. Then it acts just like a modem only and the "good" router becomes your primary router and all the features like port-forwarding work better.
 

nigelivey

Distinguished
You will want to set your current modem to "bridge mode." This will make it only work as a modem and not a router. Then you will configure your new router to be the access point.

Errr No!! If he sets his modem/router combo into bridge mode he will still need his new router to route!! What would issue IP addresses or perform NAT? An AP is essentially a L2 device similar to a switch, it knows nothing of L3 protocols such as routing or even IP!!
 

kanewolf

Titan
Moderator
Errr No!! If he sets his modem/router combo into bridge mode he will still need his new router to route!! What would issue IP addresses or perform NAT? An AP is essentially a L2 device similar to a switch, it knows nothing of L3 protocols such as routing or even IP!!
If you read the original post he says "I found a router that has dual band option of 2.4 GHz and 5Ghz " Therefore he would have a "second" router in-line so changing his ISP device to bridge mode would be appropriate.
 

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