Linux Ipsec VPN Parameters

Parameters of the /etc/ipsec.conf file

Left – Internet IP address of the left-hand side VPN device.
Leftsubnet – The network protected by the left-hand side VPN device.
Leftid – Fully qualified domain name in DNS of the left-hand side VPN device, which is preceded by an “@” sign. If DNS is set up for the IP addresses, remove this entry, because names that don’t resolve correctly cause the VPN initialization to fail.
Leftrsasigkey – The entire left RSA sig public key for the left-hand side VPN device. This can be obtained by using the ipsec showhostkey –left command.
Leftnexthop – The next hop router from the left-hand side VPN device when trying to reach the right-hand side VPN device. You may use an auto-generated variable %defaultroute, which will be valid in most cases, or the actual IP address of the next hop router in cases where the next hop is not the default router.
Right – Internet IP address of the right-hand side VPN device.
Rightsubnet – The network protected by the right-hand side VPN device.
Rightid – Fully qualified domain name in DNS of the right-hand side VPN device, which is preceded by an @ sign. If DNS isn’t set up for the IP addresses, remove this entry, because names that don’t resolve correctly cause the VPN initialization to fail.
Rightrsasigkey – The entire right RSA sig public key for the right-hand side VPN device. This can be obtained by using the ipsec showhostkey –right command.
Rightnexthop – The next hop router from the right-hand side VPN device when trying to reach the right-hand side VPN device. You may use an auto-generated variable %defaultroute, which will be valid in most cases, or the actual IP address of the next hop router in cases where the next hop is not the default router.

e.g :