VPN installation requirements

Which particular items are required to be activated on either/both the PC and the Modem for VPN to work properly:  

IPSec Pass Through  ?

PPTP Pass Through ?

L2TP Pass Through ?

Are any of the following

Application Layer Gateway Settings
required to be off or on ? :
RSVP  ?
FTP  ?
TFTP ?
Kerb88 ?
NetBios ?
Ike ?
RTSP ?
Kerb1293 ?
H225 ?
MSN ?
SIP ?
ICQ  ?
IRC666x ?
ICQTalk ?
Net2phone ?
IRC7000 ?
IRC8000 ?

IF Ping Blocking is enabled, does this prevent VPN from working?

Does VPN not work when "Hardened Mode" is on ?  i.e. with certain firewalls, security systems.?

Is VPN hindered by having the Modem set such that only specific MAC addresses can connect?

I am asking, because I like to know the requirements before I buy.   If you don't know, then ask someone

who does know, within the company.   Thank You!