Thanks for the reply.
One more question here:
When I build up the IPSec VPN (PIX 6.3), both tow PIXs use command "route outside 0.0.0.0 0.0.0.0 GatewayIP" . But if I change it to "route outside PeerIP 255.255.255.255 GatewayIP", the VPN does not come up. Do you know why?
Thanks, Leo