Hi
there, Community friends! This time, I will share with you about the introduction to VRRP Smooth Switching. Hope you like it!
After an active/standby switchover occurs on the master device, there is a period of time before the new active main board (AMB) will work normally. This period of time varies according to device and configuration. During this period, the master device cannot process VRRP packets normally, and so the backup devices cannot receive VRRP multicast packets. As a result, a backup device preempts to become the master device. Then the new master device sends a gratuitous ARP packet to the virtual IP address of each virtual router to notify the related bound modules of the status change. In preemption mode, if the original master device has a higher priority, it can preempt to become the master device again after the switchover. This causes the VRRP status to change twice, affecting service traffic.
To prevent service traffic forwarding from being affected during an AMB/SMB switchover, VRRP devices must support VRRP smooth switching.
When the AMB and SMB on a device are working properly, the master device in a VRRP backup group sends VRRP multicast packets at intervals of Advertisement_Interval. The backup device determines whether the master device works properly based on the multicast packets it receives.
During VRRP smooth switching, the master device cooperates with backup devices to ensure smooth transmission of services.
To perform VRRP smooth switching, the master device and backup devices must be enabled to learn the interval at which VRRP packets are sent. After this function is enabled:
The master device does not learn the interval at which VRRP packets are sent or check consistency of the intervals.
When a backup device receives a VRRP packet from the master device, it checks the interval in the VRRP packets. If the interval in the packet is different from the interval configured on the device, the backup device changes its own interval to the interval specified in the packet.
Switch A is configured with VRRP smooth switching. After an AMB/SMB switchover occurs and the new AMB starts, VRRP saves the currently configured interval, changes the interval of the master VRRP backup group, and sends a VRRP switching packet carrying the new interval to Switch B at the currently configured intervals.
After receiving the VRRP packet, Switch B finds that the interval carried in the VRRP packet is different the locally configured interval. Switch B then changes the local interval to the interval carried in the received VRRP packet.
After smooth switching is complete, Switch A sends a VRRP Recovery packet carrying the interval set before the AMB/SMB switchover. Switch B then learns the interval again.
When performing VRRP smooth switching, note the following:
During VRRP smooth switching, the interval learning function takes precedence over the preemption function. That is, when the interval carried in the received packet is different from the current interval and the priority carried in the received packet is lower than the current priority, VRRP first learns the interval and resets the timeout timer, and then determines whether to preempt to become the master.
VRRP smooth switching also depends on the system performance. If the system is very busy after a AMB/SMB switchover occurs and cannot schedule operations of the VRRP module, VRRP smooth switching cannot take effect.
That's all, I welcome everyone to leave a message and exchange in the comment area!
