Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 432)

414 Brocade ICX 6650 Layer 3 Routing Configuration Guide
53-1002603-01
VRRP and VRRP-E overview
Virtual router ID
A virtual router ID (VRID) consists of one Master router and one or more Backup routers. The
Master router is the router that owns the IP addresses you associate with the VRID. For this reason,
the Master router is sometimes called the “Owner”. Configure the VRID on the router that owns the
default gateway interface. The other router in the VRID does not own the IP addresses associated
with the VRID but provides the backup path if the Master router becomes unavailable.
Virtual router MAC address
Notice the MAC address associated with VRID1 in Figure 31 . The first five octets of the address are
the standard MAC prefix for VRRP packets, as described in RFC 2338. The last octet is the VRID.
The VRID number becomes the final octet in the virtual MAC address associated with the virtual
router.
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
Figure 31 , Switch 1
sends a gratuitous ARP request with MAC address 00-00-5E-00-01-01 and IP address
192.168.5.1. Hosts use the virtual router MAC address in routed traffic they send to their default
IP gateway (in this example, 192.168.5.1).
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
Figure 31 , the virtual router with
VRID1 is associated with real IP address 192.168.5.1, 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.