Fortinet FortiGate 100A, Administration Manual

Page: 275 / 374

VPN ipsec vip
FortiGate-100A Administration Guide 01-28007-0068-20041203
275
When Host_1 attempts to send a packet to Host_2 for the first time, Host_1 issues an
ARP request locally for the MAC address of Host_2. However, because Host_2
resides on a remote network, it does not respond. Instead, the FortiGate unit
responds with its own MAC address. From that point, Host_1 adds the MAC address
of the FortiGate unit to its ARP cache and the FortiGate unit will act as a proxy for
Host_2.
In the above example, the private IP addresses between the two sites have been
coordinated to protect against ambiguous routing (no two IP addresses are the same).
Setting up a configuration like this involves performing the following tasks at
FortiGate_1 and FortiGate_2.
To enable IPSec VPN communication between two network hosts that coordinate the
same private address space on physically separate networks, perform the following
tasks at the local and remote FortiGate units:
1 On both FortiGate units, define the gateway/tunnel on which to transmit VPN traffic to
the remote location (see
“Phase 1” on page 246 and “Phase 2” on page 250 ).
2 On both FortiGate units, define the firewall encrypt policy that is needed to select and
enable communication through the defined VPN gateway/tunnel (see
“Adding firewall
policies for IPSec VPN tunnels” on page 266 ).
3 Using CLI commands to configure the local FortiGate unit, add VIP entries to define
which IP addresses can be accessed at the remote end of the VPN tunnel (see
“ipsec
vip” on page 272 ). For example, to enable access to Host_2 on the HR network from
Host_1 on the Finance network, enter the following CLI commands on FortiGate_1:
config vpn ipsec vip
edit 1
set ip 192.168.12.2
set out-interface external
end
4 Using CLI commands to configure the remote FortiGate unit, add VIP entries to define
which IP addresses can be accessed at the local end of the VPN tunnel (see
“ipsec
vip” on page 272 ). For example, to enable access to Host_1 on the Finance network
from Host_2 on the HR network, enter the following CLI commands on FortiGate_2:
config vpn ipsec vip
edit 1
set ip 192.168.12.1
set out-interface external
end