Ipsec High Availability; Figure 163 Ipsec High Availability - ZyXEL Communications ZYWALL 2 PLUS User Manual

Chapter 14 IPSec VPN
If the IKE SA times out while an IPSec SA is connected, the IPSec SA stays
connected.
An IPSec SA can be set to nailed up. Normally, the ZyWALL drops the IPSec SA when the
life time expires or after two minutes of outbound traffic with no inbound traffic. If you set the
IPSec SA to nailed up, the ZyWALL automatically renegotiates the IPSec SA when the SA
life time expires, and it does not drop the IPSec SA if there is no inbound traffic.
The SA life time and nailed up settings only apply if the rule identifies the
remote IPSec router by a static IP address or a domain name. If the Remote
Gateway Address field is set to 0.0.0.0, the ZyWALL cannot initiate the tunnel
(and cannot renegotiate the SA).

14.4.2 IPSec High Availability

IPSec high availability (also known as VPN high availability) allows you to use a redundant
(backup) VPN connection to another WAN interface on the remote IPSec router if the primary
(regular) VPN connection goes down.
In the following figure, if the primary VPN tunnel (A) goes down, the ZyWALL uses the
redundant VPN tunnel (B).

Figure 163 IPSec High Availability

When setting up a IPSec high availability VPN tunnel, the remote IPSec router:
• Must have multiple WAN connections
• Only needs the configure one corresponding IPSec rule
• Should only have IPSec high availability settings in its corresponding IPSec rule if your
ZyWALL has multiple WAN connections
• Should ideally identify itself by a domain name or dynamic domain name (it must
otherwise have My Address set to 0.0.0.0)
• Should use a WAN connectivity check to this ZyWALL's WAN IP address
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ZyWALL 2 Plus User's Guide