Brocade Communications Systems FastIron SX 1600 Configuration Manual Download

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When you configure a VRID, the software automatically assigns its MAC address. When a VRID becomes active, the Master router
broadcasts a gratuitous ARP request containing the virtual router MAC address for each IP address associated with the virtual router. In

VRRP overview

on page 507, Switch 1 sends a gratuitous ARP request with MAC address 00-00-5E-00-01-01 and IP address

192.53.5.1. Hosts use the virtual router MAC address in routed traffic they send to their default IP gateway (in this example,
192.53.5.1).

Virtual router IP address

VRRP does not use virtual IP addresses. Thus, there is no virtual IP address associated with a virtual router. Instead, you associate the
virtual router with one or more real interface IP addresses configured on the router that owns the real IP addresses. In

VRRP overview

page 507, the virtual router with VRID1 is associated with real IP address 192.53.5.1, which is configured on interface e1/1/6 on
Switch 1. VRIDs are interface-level parameters, not system-level parameters, so the IP address you associate with the VRID must
already be a real IP address configured on the Owner interface.

NOTE

You can associate a virtual router with a virtual interface. A virtual interface is a named set of physical interfaces.

When you configure the Backup router for the VRID, specify the same IP address as the one you specify on the Owner. This is the IP
address used by the host as its default gateway. The IP address cannot also exist on the Backup router. The interface on which you
configure the VRID on the Backup router must have an IP address in the same subnet.

NOTE

If you delete a real IP address used by a VRRP entry, the VRRP entry also is deleted automatically.

NOTE

When a Backup router takes over forwarding responsibilities from a failed Master router, the Backup forwards traffic addressed
to the VRID MAC address, which the host believes is the MAC address of the router interface for its default gateway. However,
the Backup router cannot reply to IP pings sent to the IP addresses associated with the VRID. Because the IP addresses are
owned by the Owner, if the Owner is unavailable, the IP addresses are unavailable as packet destinations.

Master negotiation

The routers within a VRID use the VRRP priority values associated with each router to determine which router becomes the Master.
When you configure the VRID on a router interface, you specify whether the router is the Owner of the IP addresses you plan to
associate with the VRID or a Backup router. If you indicate that the router is the Owner of the IP addresses, the software automatically
sets the router VRRP priority for the VRID to 255, the highest VRRP priority. The router with the highest priority becomes the Master.

Backup routers can have a priority from 3 through 254, which you assign when you configure the VRID on the Backup router interfaces.
The default VRRP priority for Backup routers is 100.

Because the router that owns the IP addresses associated with the VRID always has the highest priority, when all the routers in the virtual
router are operating normally, the negotiation process results in the Owner of the VRID IP addresses becoming the Master router. Thus,
the VRRP negotiation results in the normal case, in which the host’s path to the default route is to the router that owns the interface for
that route.

Hello messages

Virtual routers use Hello messages for negotiation to determine the Master router. Virtual routers send Hello messages to IP Multicast
address 224.0.0.18. The frequency with which the Master sends Hello messages is the Hello interval. Only the Master sends Hello
messages. However, a Backup router uses the Hello interval you configure for the Backup router if it becomes the Master.

Brocade Communications Systems FastIron SX 1600, Configuration Manual

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