VPN IPsec site 2 site and static routing

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http://serverfault.com – I have an IPsec VPN site to site, between 2 LANs with different IP classes, LAN A is class C and LAN B is class A. The VPN presents the LAN A to LAN B with the segment. The problem is that when I start the vpn connection I cant Ping any address(LAN B remote segment) from my LAN A; I think I need some kind of static route. Could somebody help me out please? This is the situation: LAN A: real segment: local vpn segment: LAN B: remote vpn segment: Which kind of routing/natting I need to set on the LAN A router? (HowTos)