Citrix SD-WAN

Configure Virtual Router Redundancy Protocol

Virtual Router Redundancy Protocol (VRRP) is a widely used protocol that provides device redundancy to eliminate the single point of failure inherent in the static default-routed environment. VRRP allows you to configure two or more routers to form a group. This group appears as a single default gateway with one virtual IP address and one virtual MAC address.

A back-up router automatically takes over if the primary / master router fails. In a VRRP set-up, the master router sends a VRRP packet known as an advertisement to the back-up routers. If the master router stops sending the advertisement, the back-up router sets the interval timer. If no advertisement is received within this hold period, the back-up router initiates the failover routine.

VRRP specifies an election process in which, the router with the highest priority becomes the master. If the priority is the same among the routers, the router with the highest IP address becomes the master. The other routers are in backup state. The election process is initiated again if the master fails, a new router joins the group, or an existing router leaves the group.

VRRP ensures a high availability default path without configuring dynamic routing or router discovery protocols on every end-host.

Citrix SD-WAN release version 10.1 supports VRRP version 2 and version 3 to inter-operate with any third party routers. The SD-WAN appliance acts as a master router and direct the traffic to use the Virtual Path Service between sites. You can configure the SD-WAN appliance as the VRRP master by configuring the Virtual Interface IP as the VRRP IP and by manually setting the priority to a higher value than the peer routers. You can configure the advertisement interval and the preempt option.

The below network diagram shows a Citrix SD-WAN appliance and a router configured as a VRRP group. The SD-WAN appliance is configured to be the master. If the SD-WAN appliance fails, the back-up router takes-over within milliseconds, ensuring that there is no downtime.

SDW VRRP

VRRP Statistics

You can view the VRRP statistics under Monitoring > VRRP.

VRRP5

You can view the following statistics data:

  • VRRP ID: The VRRP group ID
  • Version: The VRRP protocol version.
  • Interface: The virtual interface used for VRRP.
  • State: The VRRP state of the SD-WAN appliance. It indicates whether the appliance is a master or a backup.
  • Priority: The priority of the SD-WAN appliance for a VRRP Group
  • Virtual Router IP: The virtual router IP address for the VRRP group.
  • Advertisement Interval: The frequency of VRRP advertisements.
  • Enable: Select this to enable the VRRP instance on the SD-WAN appliance.
  • Disable: Select this to disable the VRRP instance on the SD-WAN appliance.

Limitations

  • VRRP is supported in Gateway Mode deployment only.
  • You can configure up to four VRRP IDs (VRID).
  • Up to 16 virtual network interfaces can participate in VRID.

High Availability and VRRP

You can significantly reduce network downtime and traffic disruption by leveraging both the high availability and VRRP features on your SD-WAN network. Deploy a pair of Citrix SD-WAN appliance in active/standby roles along with a standby router to form the VRRP group. This group appears as a single default gateway with one virtual IP address and one virtual MAC address.

HA VRRP

The following are 2 cases with the above deployment:

1st case: High availability failover timer on SD-WAN equals the VRRP failover timer.

The expected behavior is high availability switchover to happen before the VRRP switchover, that is the traffic continues to flow through the new Active SD-WAN appliance. In this case SD-WAN continues with the VRRP Master role.

2nd case: High availability failover timer on SD-WAN greater than the VRRP failover timer.

The expected behavior is the VRRP switchover to the router happens, that is the router becomes VRRP Master and traffic might momentarily flow through the router, bypassing the SD-WAN appliance.

But once the high availability switchover happens, SD-WAN again becomes VRRP Master, that is the traffic now flows through the new active SD-WAN appliance.

For more information on high availability deployment modes, see High Availability.

Configure Virtual Router Redundancy Protocol