This article provides the information about the source and destination address in the new IP header of the tunnel mode IPSEC packet on the transit device and not on the VPN gateways.

The IPSEC packets will go encrypted over the network by not revealing the original IP header and the data. The transit devices over the network will not be able to see the original IP header and the data.

The new IP header of the packet will have source address of local VPN gateway and destination address of the remote VPN gateway.