Vrrp Operation; Selecting The Master Vrrp Router; Failover Methods - HP GbE2c - Blc Layer 2/3 Fiber SFP Option Application Manual

VRRP operation

Only the virtual router master responds to ARP requests. Therefore, the upstream routers only forward packets
destined to the master. The master also responds to ICMP ping requests. The backup does not forward any traffic, nor
does it respond to ARP requests.
If the master is not available, the backup becomes the master and takes over responsibility for packet forwarding and
responding to ARP requests.

Selecting the master VRRP router

Each VRRP router is configured with a priority between 1–254. A bidding process determines which VRRP router is or
becomes the master—the VRRP router with the highest priority.
The master periodically sends advertisements to an IP multicast address. As long as 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 will stop
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 has failed, it is clearly desirable
for the backup (or one of the backups, if there is more than one) to become the master.
NOTE: If the master is healthy but communication between the master and the backup has failed, there will
then be two masters within the virtual router. To prevent this from happening, configure redundant links to be
used between the switches that form a virtual router.

Failover methods

With service availability becoming a major concern on the Internet, service providers are increasingly deploying
Internet traffic control devices, such as application switches, in redundant configurations. Traditionally, these
configurations have been hot-standby configurations, where one switch is active and the other is in a standby mode.
A non-VRRP hot-standby configuration is shown in the figure below:
Figure 25 Non-VRRP hot-standby configuration
While hot-standby configurations increase site availability by removing single points-of-failure, service providers
increasingly view them as an inefficient use of network resources because one functional application switch sits by
idly until a failure calls it into action. Service providers now demand that vendors' equipment support redundant
configurations where all devices can process traffic when they are healthy, increasing site throughput and decreasing
user response times when no device has failed.
GbE2c high availability configurations are based on VRRP. The GbE2c software implementation of VRRP includes
proprietary extensions.
The GbE2c software implementation of VRRP supports the Active-Active mode of high availability.
High availability 146