RE: Cable Modems Need Open Ports?

["Dallas Hindle" <dallash () optushome com au>]

I think you will find that one of both of these ports are for the "heart
beat" if your ISP can't detect these or they aren't responded to, then
the isp will believe that you modem has been disconnected or not working
and you will loose your ip and connection.
You should be able to confirm this with the ISP's technical support so
you can't secure anything that isn't directly needed by you or them.


Dallas

-----Original Message-----
From: Mike Marcus [mailto:mmarcus () nelsonpub com] 
Sent: Saturday, 2 November 2002 4:53 AM
To: security-basics () securityfocus com
Subject: Cable Modems Need Open Ports?

I was "playing" with setting on my router that is connected to a cable
modem
(Comcast is the ISP).  After blocking incoming (from wan) UDP and TCP
ports
53 and 59 the router lost its external IP.  Any ideas?

Thanks,

Mike