Specifications

84 Implementing IBM System Networking 10Gb Ethernet Switches
The master periodically sends advertisements to an IPv4 Multicast address. IF the backups
receive these advertisements, they remain in the backup state. If a backup does not receive
an advertisement for three advertisement intervals, it initiates a bidding process to determine
which VRRP router has the highest priority and takes over as master.
If, at any time, a backup determines that it has higher priority than the current master does, it
can preempt the master and become the master itself, unless configured not to do so. In
preemption, the backup assumes the role of master and begins to send its own
advertisements. The current master sees that the backup has higher priority and stops
functioning as the master.
A backup router can stop receiving advertisements for one of two reasons: the master can be
down, or all communications links between the master and the backup can be down. If the
master fails, it is clearly desirable for the backup (or one of the backups, if there is more than
one) to become the master.
Failover methods
With service availability on the Internet becoming a major concern, service providers are
increasingly deploying Internet traffic control devices, such as application switches, in
redundant configurations. IBM System Networking high availability configurations are based
on VRRP. The IBM System Networking implementation of VRRP includes
proprietary extensions.
Active-active redundancy
In an active-active configuration, shown Figure 2-15, two switches provide redundancy for
each other, with both active at the same time. Each switch processes traffic on a different
subnet. When a failure occurs, the remaining switch can process traffic on all subnets.
Figure 2-15 Active-active redundancy
Virtual router group
The virtual router group ties all virtual routers on the switch together as a single entity. As
members of a group, all virtual routers on the switch (and therefore the switch itself) are in
either a master or standby state.
Two masters: If the master is healthy but communication between the master and the
backup fails, there are then two masters within the virtual router. To prevent this situation
from happening, configure redundant links to be used between the switches that form a
virtual router.