Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 805)

Multi-Service IronWare Routing Configuration Guide 777
53-1003033-02
Overview of VRRP
Master router election
Virtual routers use the VRRP priority values associated with each VRRP router to determine which
router becomes the Master. When you configure an Owner router, the VRRP priority is automatically
set to 255, the highest VRRP priority. The router in the virtual router with the highest priority
becomes the Master. Other routers become the Backup routers and can be assigned priorities from
3 through 254. The default priority value is 100.
Virtual routers use VRID Hello messages to determine if a Master router is available. They send
Hello messages to IP Multicast address 224.0.0.18 at a specified frequency. The Backup routers
wait for a duration of time for a Hello message from the Master. This duration is called the dead
interval. If a Backup router does not receive a Hello message by the time the dead interval expires,
the Backup router assumes that the Master router is dead. The Backup router with the highest
priority becomes the Master router. Once the Owner router becomes available again, it becomes
the Master router and the current Master router returns to being a Backup router.
Pre-emption
If the pre-emption feature is enabled, a Backup router that is acting as the Master can be
pre-empted by another Backup router that has a higher priority. This can occur if you add a new
Backup while the Owner is still available and the new Backup router has a higher priority than the
Backup router that is acting as the Master router.
Virtual router MAC address
When you configure a VRID, the software automatically uses the MAC address as the MAC address
of the virtual router. The first five octets of the address are the standard MAC prefix for VRRP
packets. The last octet is the VRID. For example, the MAC address for VRID is 000.5e00.0101.
When the virtual router becomes the Master router, it broadcasts a gratuitous ARP request
containing the virtual router’s MAC address for each IP address associated with the virtual router.
In
Figure 40 , Router1 sends a gratuitous ARP request with MAC address 00-00-00-00-01-01 and IP
address 192.53.5.1. Hosts use the virtual router’s MAC address in routed traffic they send to their
default IP gateway (in this example, 192.53.5.1).
Enhancements to VRRP
Brocade has enhanced VRRP by adding the following options:
• “Configuring unique virtual MAC addresses per VRID” on page 777
• “Track ports and track priority” on page 780
• “Suppression of RIP advertisements for backed-up interfaces” on page 781
• “Authentication” on page 781
• “VRRP alongside RIP, OSPF, and BGP4” on page 781
Configuring unique virtual MAC addresses per VRID
In addition to system-configured standards-based virtual MAC addresses, you can manually
configure a unique virtual MAC address for each IPv4 and IPv6 VRRP instance per VRID. For
Brocade NetIron XMR and Brocade MLX series platforms, you can configure a maximum of 2000
virtual MAC addresses.