Hi,
If you are connecting to a vpn3000 box, you can use IPSec/TCP and launch multiple connections from behind any dsl/cable router doing PAT.
if you are connecting to a PIX FW (6.3 or later), then you can connect via IPSec/UDP, and have one client connected at one time, we assume that pix is also doing PAT.
Some dsl/cable routers come with IPSec-PassThru (e.g., LinkSys), you can try those features as well, if your router supports them.
Thanks,
Afaq