Counter strike server not responding

[pooface]

I had 5 people try my server i gave them both my lan ip address and the ip address from whatismyip.com. But anyways my pc is up to date
if used thousands of guides none of it worked. Now anyways. People try to go on the server. Sometimes it shows my server and saysn ot respondign. And sometimes it doesnt show my server at all. Iportforwarded my ports. my udp port right now is 27020. I have a windows vista pc. Firewall is off. I dont even have any anti virus program. I enable steam. I pinged my ip. I forwarded the ports PortForward.com - Free Help Setting up Your Router or Firewall and my ip address is 68.72.120.214. and my ip from dedicated server is 192.168.11.2:27020.
my ipv4 address is 192.168.11.2
default gateway is 192.168.11.1
my Modem is from att
a siemens speedstream 4100 and i have a buffalo router WHR-HP-G54. I think my firmware is up to date or not. Never updated my firmware. I have 2.4 ghz processor 3 gig of ram pc-6400 800mhz
my internet speed is 1.5 mbps and upload speed is 384 kbps. Firewall is turned off. help me immidiately