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ZyWALL USG 300 User’s Guide
493
CHAPTER 33
Device HA
Use device HA and Virtual Router Redundancy Protocol (VRRP) to increase network
reliability. See Section 5.4.8 on page 117 for related information on these screens.
33.1 Virtual Router Redundancy Protocol (VRRP) Overview
Every computer on a network may send packets to a default gateway, which can become a
single point of failure. Virtual Router Redundancy Protocol (VRRP) allows you to create
redundant backup gateways to ensure that the default gateway is always available.
" The ZyWALL runs VRRP v2. You can only set up device HA with other
ZyWALLs of the same model running the same firmware version.
In VRRP, a virtual router represents a number of routers associated with one IP address, the IP
address of the default gateway. Each virtual router is identified by a unique 8-bit identification
number called a Virtual Router ID (VR ID). In the example below, Router A and Router B are
part of virtual router 10 with IP address 192.168.10.254.
Figure 363 Example: VRRP, Normal Operation
The VR ID is not shown. In normal operation, Router A is the master router. It has the same IP
address as the default gateway and forwards traffic for the network. Router B is a backup
router. It is using its management IP address 192.168.10.112. Router A sends regular
messages to Router B to let Router B know that Router A is available. The time interval
between these messages is called the advertisement interval.