Determining The Vrrp Master; Vrrp Tracking - Extreme Networks ExtremeWare XOS Guide Manual

Virtual Router Redundancy Protocol
VRRP Terms
Table 33 describes terms associated with VRRP.
Table 33: VRRP Terms
Term Description
virtual router A VRRP router is a group of one or more physical devices that acts as the default
gateway for hosts on the network. The virtual router is identified by a virtual router
identifier (VRID) and an IP address.
VRRP router Any router that is running VRRP. A VRRP router can participate in one or more virtual
routers. A VRRP router can be a backup router for one more master routers.
IP address owner A single VRRP router that has the IP address of the virtual router configured as its real
interface address. The IP address owner responds to TCP/IP packets addressed to the
virtual router IP address. The IP address owner is optional in a VRRP configuration.
master router The physical device (router) in the virtual router that is responsible for forwarding
packets sent to the virtual router, and responding to ARP requests. The master router
sends out periodic advertisements that let backup routers on the network know that it is
alive. If the IP address owner is identified, it always becomes the master.
backup router Any VRRP router in the virtual router that is not elected as the master. The backup
router is available to assume forwarding responsibility if the master becomes
unavailable.
VRID Virtual router identifier. Each virtual router is given a unique VRID. All of the VRRP
routers that participate in the virtual router are assigned the same VRID.
virtual router MAC RFC 2338 assigns a static MAC address for the first 5 octets of the virtual router.
address These octets are set to 00-00-5E-00-01. When you configure the VRID, the last octet of
the MAC address is dynamically assigned the VRID number.

Determining the VRRP Master

The VRRP master is determined by the following factors:
• VRRP priority—This is a user-defined field. The range of the priority value is 1 to 254; a higher
number has higher priority. The value of 255 is reserved for a router that is configured with the
virtual router IP address. A value of 0 is reserved for the master router, to indicate it is releasing
responsibility for the virtual router. The default value is 100.
• Higher IP address—If the routers have the same configured priority, the router with the higher IP
address becomes the master.

VRRP Tracking

Tracking information is used to track various forms of connectivity from the VRRP router to the outside
world. ExtremeWare XOS supports the use of VRRP route table tracking.
You can configure VRRP to track specified routes in the route table as criteria for failover. If any of the
configured routes are not available within the route table, the router automatically relinquishes master
status and remains in backup mode.
To add or delete a tracked route, use the following command:
config vrrp vlan <vlan_name> vrid <vridval> [add | delete] track-iproute
<ipaddress>/<masklength>
166 ExtremeWare XOS 10.1 Concepts Guide