To whom may read this:
For awhile now I have been trying to figure out this problem with my Cisco 678 DSL Modem and my Linksys Etherfast DSL Router (BEFSR41). My Linksys Router is also a NAT and has firewall capabilities such as opening and blocking certain ports, static internal IP's and so on... I am not able to host games on any game or send files through MSN Messenger and occasionally through AOL Instant Messenger. Even if I do open the necesarry ports on my Linksys they still don't work. I figure that the problem lies in my Cisco 678 Modem and that it is somewhat of a firewall. I think I need to disable that function through the command line while directly connected via the management port. I have no idea what setting that may be or if that is the problem at all. I do not use a software side firewall.
Personal Computer specifications:
Pentium 3 900Mhz
Western Digital 7200RPM 80GB HD
CD-RW and DVD drive
Cisco Systems Cisco 678 DSL Modem
Linksys EtherFast Cable/DSL Router (NAT/BEFSR41)
Altec Lansing 641 4.1 Speaker system
Windows XP Professional SP1 (Firewall Disabled)
Qwest DSL (640 UP/256 DOWN)
Thank you for your help and support.