Fault tolerance shows several different ways a route might be recovered
after an outage.
Another use for virtual IP addresses is to protect against route fault
tolerance.
This example shows several different ways a route can be recovered after
an outage. The most reliable connection is when a virtual IP address is defined
on the system. With virtual IP's support, even if an interface fails, the
session can still communicate using different interfaces.
![Fault tolerance](rzajw512.gif)
What happens if router R1 fails?
- Connections through R1 are rerouted through R2.
- The failed gateway will detect R1 recovery, but active connections will
continue to run through R2.
What happens if interface 10.1.1.1 fails?
- Active connections to 10.1.1.1 are lost, but other connections to 10.1.1.2,
10.1.1.3, and 10.2.1.1 remain.
- Route rebinding:
- Pre-V4R2: Indirect routes are rebound to 10.1.1.2 or 10.1.1.3.
- V4R2: Routes are rebound only if Preferred Binding Interface is set to
NONE.
- V4R3 and higher: You need to define 10.2.1.1 as the virtual IP address
and primary system address.
- The primary IP address of the system remains active.
- The system stays accessible as long as at least one physical interface
remains active.