I've tried & tried. Can't get a wireless router to work with a cable modem-any ideas

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

Sometimes if I have problem getting an IP address assigned by DHCP I'll do it manually:

Make sure the subnet mask is 255.255.255.0 so the full range of IP addresses is available, then assign manually an IP address to your laptop and see if you can connect (under Network Connections). Make sure the router IP address is also the default gateway.

Is it a LAN or WLAN problem, or both?

...oh, and is the modem and router 2 seperate devices, or is it one device?

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

It's one of the less appealing problems to troubleshoot. I usually start by completely power cycling the modem, then connecting a PC directly to the modem and checking to see if I can successfully obtain DHCP lease, then checking to see if I can connect to the internet (basically that the gateway & DNS servers are working properly).

If that all works, the second step is to try again with the router. I start by resetting the router to factory defaults using the little pinhole and configuring from scratch. In most cases that was sufficient, one time I did have to clone the MAC. BTW, if the modem has a hardware reset switch, I would use it as well.

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

Yea, like dmapr said, try connecting your laptop directly to the cable modem and see if you can connect. If you know the IP address of the cable modem, type it in a web browser and see if you can access the modems GUI and have a look around at the settings. Also try giving the router a fixed IP address within the modems subnet.

...oh, also if the modem is the DHCP, make sure DHCP is disabled on the router, as 2 DHCP servers on the same subnet will cause things to go haywire...

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

If your cable modem includes VoIP service (look for the RJ-11s on the back), there should a backup battery. Removing that can make it "forget" the MAC address of the computer it knows, and accept the default MAC of your router, connected next. I am somewhat familiar with competitor Comcast's hardware here in Memphis.

Who is your cable supplier, and what model number is on their supplied hardware?

COtech

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

Jay, RadioRaiders is right in the sense that *if* both the modem & the router have the same subnet then the packet routing will fail at some point. However, just because both the modem & the router are in DHCP mode it doesn't mean that this is the case. Typically modems and routers will have different default subnets for this very reason, but one very simple way to avoid this is to change the router's IP address from 192.168.x.x to 10.x.x.x — I've never seen a cable modem with a 10.x.x.x subnet. This way both devices can be left in DHCP mode.

Also, the router will have some diagnostic utilities built-in accessible from one of the admin pages, you may want to check those and see if they have anything useful to report.

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

What sort of address range are you seeing assigned to the computer attached to the cable modem? The following ranges of address are allowed for private LANs, separated by a gateway router from the Internet:

10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.25.255 (you seem familiar with this range, with room for 254 laptops)

If you saw 169.254.?.?, you don't have a good connection (set up with a wired PC!). That's a default address the OS fills in the blanks with when nothing useful is received.

COtech

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

Is that the one you get from the cable modem or from the router? At any rate, at least for the troubleshooting I would not use it, I'd stick to 255.255.255.0.

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

What's the IP address that you get from the cable modem when you connect your PC directly?

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

That is really weird that the cable company limits the subnet you can use inside your house The modem gets an external IP address (ie: "internet" IP address) but then the internal IP address (ie: your LAN IP address) should be whatever you want it to be within the private IP address range (like 192.xxx.etc) But by forcing you to use a /29 subnet (255.255.255.248) they are saying that your DHCP can only assign 6 IP addresses inside your house. Why would they want to do that? :headscrat ...is it something unique to cable? I've always used DSL and was always able to set my internal LAN IP address and subnet to whatever I want...

To clarify what I meant, is that 2 DHCP servers can't serve the same IP address range.

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

You're working under assumption that the cable modem has NAT and it's DHCP server gives out private IP addresses. This doesn't have to be the case (and usually is not the case unless the modem has a built-in router) — you can be given a public IP address. Also, Jay said the subnet was 255.255.248.0, not 255.255.255.248 — which would be in line with a public IP address. On my DSL line I have several static IP addresses and my subnet mask is 255.255.248.0.

Of course not — but it seemed like you implied that both modem and router would be using the same IP range and I just wanted to point out that in my experience it was never the case (unless the modem was a modem/router combo, but then you don't need a second router behind it).

 

Re: I've tried & tried. Can't get a wireless router to work with a cable modem-any i

Jay2, Until more info can be found, try what we discovered in the Alltel forum setting up a USB radio to a PC with MS Internet Connection Sharing on. Keep that DHCP on.

Remember that a wireless router is three devices in one box:

A six-port switch (two internal ports go to the LAN side of router and the wireless access point radio).
A router with one side to the switch, and the other to the external WAN RJ-45.
A WAP radio connected to the switch internally.

Don't use the router. Cable from the modem to one of the LAN switch ports 1 to 4, and from there to the rest of your wired devices. Not much room for wireless company if you are limited to six LAN IP addresses.

COtech