Router blind to working IP phone?

February 27, 2006 11:01 AM

Why in the hell does my DHCP router (Linksys WRT54G) not actually see my IP phone?

I have a proprietary VoIP phone which my company manufactures, and it's connected through my router to the 'Net. And everything works fine.

The link is like this:

'Net -> Motorola Cablemodem (from Comcast) -> Linksys.

Phone is plugged directly into router.

When I pull up the Local Network tab on the admin utility, it shows all of my other computers on the DHCP Tables tab, but the phone doesn't exist there.

Yet it works. Why is this? Is it the fact that the phone doesn't have a hostname? It should still show the lease on the IP address, right?

I only ask because I might need to make alterations to the network, adjust certain ports, etc, but I can't SEE it to adjust it if I need to.

Stupid router.

posted by TeamBilly to computers & internet (10 comments total)

Are you sure your phone adapter is using DHCP to get its IP address?
posted by Ethereal Bligh at 11:20 AM on February 27, 2006

Yes, EB - absolutely. Here's the really weird part, but it wasn't applicable to the OP - at the far end (a server which lives in Atlanta) I can see the phone and the private IP address from my own network. But it doesn't show locally on the Linksys. Weird.
posted by TeamBilly at 11:22 AM on February 27, 2006

Do you have logging running? Make a call, sniff the UDP traffic, see what IP address your phone is using.
posted by meehawl at 11:22 AM on February 27, 2006

Maybe the lease expired and it just kept its address or something. Shrug.
posted by cellphone at 11:23 AM on February 27, 2006

It probably doesn't list any DHCP clients that don't have a Windows (SMB) hostname. I've seen some routers like that.
posted by kindall at 11:30 AM on February 27, 2006

What others have said, and also it sounds like maybe it's at the DMZ address, too.

You don't need the IP address it's using so much as you need the eth number. What you want to do is to define a DHCP setting for that ethernet address, then see if it's set to that when you reboot your phone adapter. If you give it a hostname there, it will report that to its connection monitor, probably.

My VOIP adapter has a web interface. Does yours?
posted by Ethereal Bligh at 12:03 PM on February 27, 2006

Also, starting pinging addresses from 192.168.1.100 on. If it's on DHCP, it should be one of the first few of those, if you haven't changed the DHCP settings.
posted by cellphone at 12:33 PM on February 27, 2006

I have what I think is a similar problem with my Primus TalkBroadband gateway. It turns out the box is designed so that you can only connect to it when it's plugged directly into the computer. I cannot access it via a PC on my local network.
posted by Gortuk at 12:45 PM on February 27, 2006

p.s. Regarding logging. LinkLogger for Linksys WRT is a great program and the trial edition will run for a while and show you more details about your network than you probably ever would want to know.
posted by meehawl at 1:52 PM on February 27, 2006

Well, I know the IP address of the phone, it just bothers me that it doesn't show up in the list of DHCP devices.

Thanks for the tips. I suspect it's a case of the hostname missing.

EB - there isn't a web client in the sense that you ask - this is part of a PBX - it's not something like Vonage or Broadwing.

You can safely dial 9-1-1 on ours. :-)
posted by TeamBilly at 3:47 PM on February 27, 2006