The physical routers are assigned to the virtual routers by means of the router ID that is specified when defining the virtual router. All devices in which virtual routers are created with the same router ID form a "standby group" in which the devices act as replacements for one another. There are three different examples of standby groups:
- In a simple backup scenario, two or more routers form one standby group. A virtual router with the same router ID and the same virtual IP address is configured in all physical routers (item 1 in the following illustration).
- In order to perform load balancing, the same number of virtual routers with differing IDs and IPs are defined as there are physical routers planned for the VRRP group. For example, two devices would each belong to two standby groups (2).
- It is also possible to create more complex combinations with many devices. For example, two devices can form their own standby group with router ID 1 and two other devices can form another group with the ID 2 (3). Depending on the requirements, it is also possible to selectively assign certain devices to a single group while other devices remain members of all groups (4).
