Description of the Network Topology for the IPsec Tasks to Protect a VPN

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The procedures in this section assume the following setup. For a depiction of the network, see Sample VPN Between Offices Connected Across the Internet.

Each system is using an IPv4 address space.

These procedures also work with IPv6 addresses or a combination of IPv4 and IPv6 addresses.
Each system has two interfaces. The net0 interface connects to the Internet. In this example, Internet IP addresses begin with 198.51.100. The net1 interface connects to the company's LAN, its intranet. In this example, intranet IP addresses begin with the number 192.0.2.
Each system requires ESP encryption with the AES algorithm. The AES algorithm uses a 128-bit or 256-bit key.
Each system requires ESP authentication with the SHA-2 algorithm. In this example, the SHA-2 algorithm uses a 512-bit key.
Each system can connect to a router that has direct access to the Internet.
Each system uses shared security associations.

The following illustration shows the configuration parameters used in the procedures.

Figure 13 Sample VPN Between Offices Connected Across the Internet

The configuration parameters are listed in the following table.

Parameter	Europe	California
System name	euro-vpn	calif-vpn
System intranet interface	net1	net1
System intranet address, the default route to the other network	192.0.2.36	192.0.2.3
System intranet address object	net1/inside	net1/inside
System Internet interface	net0	net0
System Internet address	198.51.100.6	198.51.100.33
Name of Internet router	router-E	router-C
Address of Internet router	198.51.100.1	198.51.100.31
Tunnel name	tun0	tun0
Tunnel name address object	tun0/v4tunaddr	tun0/v4tunaddr