Possibly the most important application of VRRP is the provision of backup connections in which one or more routers serve as backup for the main router. These routers can use different physical media for the Internet connection, such as DSL in the main router and UMTS or ISDN in the backup routers. A normal backup chain thus resembles the following:
- If the DSL connection fails 1, the UMTS router 2 takes over the function.
- If the UMTS connection 2 fails, the ISDN router 3 takes over the function.
Since almost all LANCOM devices with a DSL interface also have an ISDN interface, the main router can also take over ISDN backup functions at the end of the backup chain—as long as the hardware does not fail completely.
