Any expected troubles in this wireless network setup?

The present setup is a standard cable modem with one wired LAN port, that goes into a cat 5 cable that runs a long way to a wired switch which feeds a wired network, and may contain a firewall, even if NAT (not sure yet)

The plan is to add a wireless router near and plugged into the LAN port of the cable modem, this will allow wireless devices to connect in that area, and plug the long Cat 5 cable to the switch into one of the LAN ports in the wireless router.

I want to verify if I should expect the present wired LAN to continue to work properly even though it is now through the wireless router instead of directly into the cable modem.


That should work fine.

I assume that there is really only one public IP address for the cablemodem, so something within your building is issuing local IP addresses. It would be wise to figure out where everything is getting IP addresses.

How about the make and model of the cable modem and network switch?
What other network gadgets share the wired lan?

If you are setting up a basic network from scratch then Cablemodem => WIFI Router => Wired Switch is a perfectly normal configuration, as long as the cablemodem is not a router itself. And even if it is, there are ways to get around this.

If your switch is “dumb” (i.e. it does no routing on its own) than this should work fine. If it’s “smart”, then you might have problems but I still wouldn’t expect any. And it’s probably dumb.

In your current setup it sounds like the cable modem is also a router. If your wired switch is the router, then everything I’m going to say is wrong. If the cable modem has more than one ethernet port, then it is almost definitely a router.

You have two options for the way things will work:
Cable modem/router —> Wireless/wired —> wired switch
Cable modem —> Wireless/wired/router —> wired switch
(each —> represents a physical cable.)

My suggestions is to use your existing router, and reconfigure the new piece of equipment to behave the way you want. Instead of using the uplink/WAN connection port on the wireless router, just use one of the internal/LAN ports to connect to the cable modem. This will allow the cable modem to continue acting like a router, doing NAT and handing out IP addresses. The wireless router will essentially become a wired switch, which happens to have a wireless base station, too. You might have to do some configuration on the wireless router so that it has an IP address that is accessible from the inside of your network. That’s not strictly necessary for the wireless router to function, but it will help when you want to connect to it and manage it. You will also want to disable the DHCP server on the wireless router. If you have two DHCP servers on the network, that will be bad.

Be sure and realize, my suggested method is creating a single internal network that spans both wired and wireless. If you care at all about security, be sure and enable WPA2 security on the wireless side. There are a variety of other arrangements you can do that would have wireless on its own network, which could be firewalled from your wired network, but that quickly gets complicated.