Getting self-assigned ip address from Comcast modem

brainwave89 · Jun 18, 2008

When I hook up an ethernet connection from my Comcast modem to my Mac Pro and PowerBook G4 I end up getting an self-assigned ip address (169.254.x.x). When I hook up an ethernet connection to my Dell Dimension desktop from the cable modem I have no problem getting online.
I have shut off the modem at various times from 30 seconds to 4 minutes before I plugged it back in with the same result on the Macs.
I would love to hook up my Airport Extreme to the cable modem but I would be happy just to get this resolved first.

Once or twice I was able to get an 192.168.x.x ip address on the mac's before it switched to 169.254.x.x.
Any suggestions to get this resolved would be appreciated.
Thanks for looking.

NH MacGuy · Jun 18, 2008

This also happened to me...

on my Powerbook G4, running 10.5.3 Here is what ultimately worked...

Unplug computer from modem
Restart computer
Open System Preferences, choose Security, then select the firewall tab.
Select "Allow all incoming connections" & Close system preferences.

Now, connect your Mac to the network (either wirelessly or via ethernet)

Hopefully it will now receive a router-assigend ip. Once connected, I would go back to System Preferences & select a safer level of firewall security.

I was prompted to try this after reading somewhere that this was a Leopard/Firewall bug.

Hope this helps.

Tom

brainwave89 · Jun 18, 2008

Thanks for your help.

The firewall setting is set to "Allow all incoming connections" already. The Mac Pro is running 10.5.0 and my PowerBook G4 is running 10.5.3.
Urgh..

apfhex · Jun 18, 2008

brainwave89 said:
When I hook up an ethernet connection from my Comcast modem to my Mac Pro and PowerBook G4

Can you clarify exactly how your devices are hooked up, starting from the modem? What are your network settings on the Macs?

It should be something like this: Modem -> Airport router -> your computers. The router will be assigned an external IP from the modem. The computers will be assigned a local IP from the router. I don't see how with this setup your Macs would be configuring themselves with anything but the IP given from the router.

The OS X firewall shouldn't have anything to do with it.

brainwave89 · Jun 18, 2008

Thank you apfhex.

An Ethernet cable is coming from the Linksys Cable modem and was hooked up directly to both of the Macs at different times.
In System Preferences > Network the built-in Ethernet has the following settings on both computers:
Location: Automatic
Configure: Using DHCP

The PowerBook G4 had never previously attempted to get online with the Linksys Cable Modem. The Mac Pro had.

Please let me know if I missed any pertinent information.

grapes911 · Jun 18, 2008

1. Did the router run out of IP addresses to give out? Make sure you don't have your address range set to something like 192.168.1.1 though 192.168.1.2.

2. Do you have any MAC filtering on?

operator207 · Jun 19, 2008

MAC address filtering done on the Comcast end of your connection. It will allow X MAC addresses from an account, X+1 will not work and so on.

If X = 5, you can have 5 devices on their network, after that you have to call them and either have them delete old MAC Addresses, or have them delete all of them, and start over.

They used to allow only 1 unless you called them and asked for more. That is one of the reasons every soho home router has "MAC address spoofing".

I would bet if you called and talked to a knowledgeable Comcast tech, you could get them to tell you if your full up on MAC addresses.

brainwave89 · Jun 19, 2008

Thank you operator207. I will contact Comcast tomorrow.

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Getting self-assigned ip address from Comcast modem

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