The Virtual Router Redundancy Protocol (VRRP) is a computer networking protocol that provides for automatic assignment of available Internet Protocol (IP) routers to participating hosts. This increases the availability and reliability of routing paths via automatic default gateway selections on an IP subnetwork.
Virtual Router Redundancy Protocol (VRRP) is a non-proprietary redundancy protocol described in RFC 3768 designed to increase the availability of the default gateway servicing hosts on the same subnet. This increased reliability is achieved by advertising a “virtual router” (an abstract representation of master and backup routers acting as a group) as a default gateway to the host(s) instead of one physical router. Two or more physical routers are then configured to stand for the virtual router, with only one doing the actual routing at any given time.
If the current physical router that is routing the data on behalf of the virtual router fails, an arrangement is made for another physical router to automatically replace it. The physical router that is currently forwarding data on behalf of the virtual router is called the master router. Physical routers standing by to take over from the master router in case something goes wrong are called backup routers.
VRRP enables hosts on a LAN to make use of redundant routing platforms on that LAN without requiring more than the static configuration of a single default route on the hosts. The VRRP routing platforms share the IP address corresponding to the default route configured on the hosts
Figure 1 illustrates a basic VRRP topology. In this example, Routers A, B, and C are running VRRP and together make up a virtual router. The IP address of this virtual router is 10.10.0.1 (the same address as the physical interface of Router A).
Figure 1: Basic VRRP
Because the virtual router uses the IP address of the physical interface of Router A, Router A is the primary VRRP router, while routers B and C function as backup VRRP routers. Clients 1 through 3 are configured with the default gateway IP address of 10.10.0.1. As the primary router, Router A forwards packets sent to its IP address. If the primary virtual router fails, the router configured with the higher priority becomes the primary virtual router and provides uninterrupted service for the LAN hosts. When Router A recovers, it becomes the primary virtual router again.
Note:
In some cases, during an inherit session, there is a small time frame during which two routers are in Primary-Primary state. In such cases, the VRRP groups that inherit the state do send out VRRP advertisements every 120 seconds. So, it takes the routers up to 120 seconds to recover after moving to Primary-Backup state from Primary-Primary state.
ACX series routers can support up to 64 VRRP group entries. These can be a combination of IPv4 or IPv6 families. If either of the family (IPv4 or IPv6) is solely configured for VRRP, then 64 unique VRRP group identifiers are supported. If both IPv4 and IPv6 families share the same VRRP group, then only 32 unique VRRP identifiers are supported.
Note:
ACX Series routers support VRRP version 3 for IPv6 addresses.
ACX5448 router supports RFC 3798 VRRP version 2 and RFC 5798 VRRP version 3. ACX5448 router also supports configuring VRRP over aggregated Ethernet and integrated routing and bridging (IRB) interfaces.
The following limitations apply while configuring VRRP on ACX5448 router:
- Configure a maximum of 16 VRRP groups.
- Interworking of VRRP version 2 and VRRP version 3 is not supported.
- VRRP delegate processing is not supported.
- VRRP version 2 authentication is not supported.
Figure 1 illustrates a basic VRRP topology with EX Series switches. In this example, Switches A, B, and C are running VRRP and together they make up a virtual routing platform. The IP address of this virtual routing platform is 10.10.0.1 (the same address as the physical interface of Switch A).
Figure 2: Basic VRRP on EX Series Switches
Figure 3 illustrates a basic VRRP topology using Virtual Chassis configurations. Switch A, Switch B, and Switch C are each composed of multiple interconnected Juniper Networks EX4200 Ethernet Switches. Each Virtual Chassis configuration operates as a single switch, which is running VRRP, and together they make up a virtual routing platform. The IP address of this virtual routing platform is 10.10.0.1 (the same address as the physical interface of Switch A).
Figure 3: VRRP on Virtual Chassis Switches
Because the virtual routing platform uses the IP address of the physical interface of Switch A, Switch A is the primary VRRP routing platform, while Switch B and Switch C function as backup VRRP routing platforms. Clients 1 through 3 are configured with the default gateway IP address of 10.10.0.1 as the primary router, Switch A, forwards packets sent to its IP address. If the primary routing platform fails, the switch configured with the higher priority becomes the primary virtual routing platform and provides uninterrupted service for the LAN hosts. When Switch A recovers, it becomes the primary virtual routing platform again.