Airport/Cable Modem Help 2

[skymut]

This is a long one, so please bear with me.

Okay, I have an ibook to use through the summer, as well as an airport. Now I've been using 4 airports at work just fine, so this one is perplexing.

At home, I have high speed internet connectivity via cable modem. I have not been given a static IP address, ALL internet information is handed out via dhcp. On my PC, everything works great (it is 'hard wired' into a hub).

So, I set the airport up to connect to the internet via the ethernet port, and to get info from dhcp. I also set the airport up to NAT. Well, the airport obviously isn't getting the info via dhcp, it is defaulting to a 10.0.1.1 address.

I even went so far as to get on my pc, ping until I found and address not in use, manually configure the airport with the valid ip address, dns server, domain etc. Still can't get out.

I'm an assistant network admin in a fairly large network environment, so I'm pretty solid with troubleshooting. I've looked at this from every angle (yes, even at the physical layer-I tested my cable). I'm a lot more familiar with windows, but I do support many macs, and have configured 4 airports that work splendidly at work.

All this to say, I would rather ask some folks who know something, than call my ISP's helpdesk who will probably read through a series of steps from some manual.

Any thoughts?

 

[robbLA]

Does your cable company Tie your MAC address to the cable modem? Mine does, and I have to use LinkSys routers that allow me to fake the AP's MAC address.

Also, when Airport first came out, AT&T cable modems were set to not allow any of the MAC addresses (but I think that they have lightened up these days.)

If your Airport is not getting a valid IP, then this is likely what's going on...

-r --
robb

 

[skymut]

Good call robbLA.
When the cable modem first powers up, it binds the ip config info to the first ethernet interface that requests it. Anything after that is hosed.
What threw me off was that the documentation said that you could just add a hub or switch, config all ethernet interfaces to dhcp and go. Don't believe everything you read, huh?
Anyway, I resolved it with a linksys router, and all ethernet interfaces are happy.
Thanks.

 

[macigor]

Can we get some more details here, please ? I have a set up with an Airport Base Station, Toshiba cable modem and Comcast ISP. This all worked great until about three weeks ago and now the ABS cannot hold onto an IP address. If I remove the ABS and connect my computer directly to the cable modem, the connection is fine, but I now cannot run all 3 computers in my house from the one connection.

I want to understand this problem/issue. Is it the hardware, the software, or the ISP causing trouble ? I would bet money that Comcast changed something in their end of the setup, but them I tend to grumble a lot.
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." Calvin (Bill Watterson)