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Chapter 20 IPSec VPN
ZyWALL 110/310/1100 Series User’s Guide
310
Extended Authentication
Extended authentication is often used when multiple IPSec routers use the same VPN tunnel to
connect to a single IPSec router. For example, this might be used with telecommuters.
In extended authentication, one of the routers (the ZyWALL or the remote IPSec router) provides a
user name and password to the other router, which uses a local user database and/or an external
server to verify the user name and password. If the user name or password is wrong, the routers
do not establish an IKE SA.
You can set up the ZyWALL to provide a user name and password to the remote IPSec router, or
you can set up the ZyWALL to check a user name and password that is provided by the remote
IPSec router.
If you use extended authentication, it takes four more steps to establish an IKE SA. These steps
occur at the end, regardless of the negotiation mode (steps 7-10 in main mode, steps 4-7 in
aggressive mode).
Certificates
It is possible for the ZyWALL and remote IPSec router to authenticate each other with certificates.
In this case, you do not have to set up the pre-shared key, local identity, or remote identity because
the certificates provide this information instead.
• Instead of using the pre-shared key, the ZyWALL and remote IPSec router check the signatures
on each other’s certificates. Unlike pre-shared keys, the signatures do not have to match.
• The local and peer ID type and content come from the certificates.
Note: You must set up the certificates for the ZyWALL and remote IPSec router first.
IPSec SA Overview
Once the ZyWALL and remote IPSec router have established the IKE SA, they can securely
negotiate an IPSec SA through which to send data between computers on the networks.
Note: The IPSec SA stays connected even if the underlying IKE SA is not available
anymore.
This section introduces the key components of an IPSec SA.
Local Network and Remote Network
In an IPSec SA, the local network, the one(s) connected to the ZyWALL, may be called the local
policy. Similarly, the remote network, the one(s) connected to the remote IPSec router, may be
called the remote policy.
Active Protocol
The active protocol controls the format of each packet. It also specifies how much of each packet is
protected by the encryption and authentication algorithms. IPSec VPN includes two active
protocols, AH (Authentication Header, RFC 2402) and ESP (Encapsulating Security Payload, RFC
2406).