Site to site VPN between Cisco VPN Router and Sonicwall NAT issues

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http://serverfault.com – I'm trying to establish a site-to-site VPN connection from office to datacenter. Cisco RV042G and SonicWall NSA2400 In the office; we have the subnet defined and hosts from to defined (.150 being the router) In the datacenter; I have an interface (X4) that is setup for network (.1 being the interface). I can sucessfully establish the VPN connection; but then I can't reach the datacenter (for example by pinging which is a server). Ideally i'd like to map our office to the same subnet on datacenter. So would (HowTos)