[CLUE-Tech] Access to ATT Cable systems? (more)

[Dave Price]

On Tue, Oct 22, 2002 at 10:19:25AM -0600, Jeffrey Brown wrote:
> I am using AT&T's cable modem service and have successfully set up
> access to services behind my firewall w/ NAT and port redirection. 
> 
> 1) AT&T's DHCP service occasionally offers different IP addresses, you
> might verify the IP address hasn't changed. 
> 
> 2) Check and see if the router/firewall is blocking ICMP traffic, if
> this is the case ping and traceroute will not work, although the host
> may be active on the network. Try NMAP to scan the host: 
> $ nmap -v -sS -O -P0 <host>  # Scans TCP ports, must be run as root, 
> -P0 option doesn't employ ICMP to check whether the host is "alive"
> $ nmap -v -sU -P0 <host>  # Scans UDP ports
> 
> 3) What obtains the IP address? The router or the host? How is NAT
> setup? 
> 
> 4) Beyond that I'd start troubleshooting from the 12.254.89.67 host.
> 
The two hosts in question are

12-254-89-67.client.attbi.com &
12-254-88-143.client.attbi.com 

.67 is a lynksys router - i got it's ip from the router's admin screen,
and confirmed by trying to telnet to my home system and looking at the
syslog.

.143 is in another home and is a single PC connected directly to the
cable modem.  Address obtained by winipcfg and remote syslog traces.

When I traceroute, I only get as far as the ATT head-end router for the
host in question - then nothing.

In each house, I can do 'self-pings', so ICMP should work from outside
if ATT routing is right.

I will bring a linux laptop on site and do a bit more playing, but I was
hoping someone might have some hints about ATT's routing setup...

aloha,
dave