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Understanding VRRP on EX Series Switches

Overview of VRRP on EX Series Switches

You can configure the Virtual Router Redundancy Protocol (VRRP) or VRRP for IPv6 on Gigabit Ethernet interfaces, 10-Gigabit Ethernet interfaces, and logical interfaces on EX Series switches. When VRRP is configured, the switches act as virtual routing platforms. 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. At any time, one of the VRRP routing platforms is the master (active) and the others are backups. If the master routing platform fails, one of the backup routing platforms becomes the new master, providing a virtual default routing platform and enabling traffic on the LAN to be routed without relying on a single routing platform. Using VRRP, a backup EX Series switch can take over a failed default switch within a few seconds. This is done with minimum loss of VRRP traffic and without any interaction with the hosts. Virtual Router Redundancy Protocol is not supported on management interfaces.

VRRP for IPv6 provides a much faster switchover to an alternate default routing platform than IPv6 Neighbor Discovery (ND) procedures. VRRP for IPv6 does not support the authentication-type or authentication-key statements.

Note: Do not confuse the VRRP master and backup routing platforms with the master and backup member switches of a Virtual Chassis configuration. The master and backup members of a Virtual Chassis configuration compose a single host. In a VRRP topology, one host operates as the master routing platform and another operates as the backup routing platform, as shown in Figure 2.

Switches running VRRP dynamically elect master and backup routing platforms. You can also force assignment of master and backup routing platforms using priorities from 1 through 255, with 255 being the highest priority. In VRRP operation, the default master routing platform sends advertisements to backup routing platforms at regular intervals. The default interval is 1 second. If the backup routing platforms do not receive an advertisement for a set period, the backup routing platform with the highest priority takes over as master and begins forwarding packets.

Note: Priority 255 cannot be set for routed VLAN interfaces (RVIs).

VRRP is defined in RFC 3768, Virtual Router Redundancy Protocol.

Examples of VRRP Topologies

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 1: Basic VRRP on EX Series Switches

Figure 2 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 2: 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 master 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 master router, Switch A, forwards packets sent to its IP address. If the master routing platform fails, the switch configured with the higher priority becomes the master virtual routing platform and provides uninterrupted service for the LAN hosts. When Switch A recovers, it becomes the master virtual routing platform again.