When 192.168.1.2 initiates a packet to 192.168.2.3, it is send to R1. This would have the

source IP address in the IP header as 192.168.1.2 and destination IP address as

192.168.2.3. When the packet reaches R1, an additional header is added which would

have the source IP address as S0 (R1) and destination IP address as S1 (R2). When the

packet reaches R2, the outer header is discarded and the inner header which is the actual

header would contain the source IP address as 192.168.1.2 and destination as the actual

destination IP address which is 192.168.2.3. So when the packet reaches 192.168.2.3, it

would have its IP address as the destination IP address.