Vrrp And Stg - Avaya 8800 Planning And Engineering

The VRRP BackupMaster uses the VRRP standardized backup switch state machine. Thus,
VRRP BackupMaster is compatible with standard VRRP.
When implementing VRRP, follow the Avaya recommended best practices:
• Do not configure the virtual address as a physical interface that is used on any of the
routing switches. Instead, use a third address, for example:
- Interface IP address of VLAN a on Switch 1 = x.x.x.2
- Interface IP address of VLAN a on Switch 2 = x.x.x.3
- Virtual IP address of VLAN a = x.x.x.1
• Set the VRRP hold down timer long enough such that the IGP routing protocol has time
to converge and update the routing table. In some cases, setting the VRRP hold down
timer to a minimum of 1.5 times the IGP convergence time is sufficient. For OSPF, Avaya
recommends that you use a value of 90 seconds if using the default OSPF timers.
• Implement VRRP BackupMaster for an active-active configuration (BackupMaster works
across multiple switches participating in the same VRRP domain.
• Configure VRRP priority as 200 to set VRRP Master.
• Stagger VRRP Masters between Ethernet Routing Switches in the core.
• Take care when implementing VRRP Fast as this creates additional control traffic on the
network and also creates a greater load on the CPU. To reduce the convergence time of
VRRP, the VRRP Fast feature allows the modification of VRRP timers to achieve sub-
second failover of VRRP. Without VRRP Fast, normal convergence time is approximately
3 seconds.
• Ensure that both SMLT aggregation switches can reach the same destinations by using
a routing protocol. For routing purposes, configure per-VLAN IP addresses on both SMLT
aggregation switches.
• Introduce an additional subnet on the IST that has a shortest-route-path to avoid issuing
Internet Control Message Protocol (ICMP) redirect messages on the VRRP subnets. (To
reach the destination, ICMP redirect messages are issued if the router sends a packet
back out through the same subnet on which it is received.)
• Do not use VRRP BackupMaster and critical IP at the same time. Use one or the other.
• When implementing VRRP on multiple VLANs between the same switches, Avaya
recommends that you configure a unique VRID on each VLAN.

VRRP and STG

VRRP protects clients and servers from link or aggregation switch failures. Your network
configuration should limit the amount of time a link is down during VRRP convergence. The
following figure shows two possible configurations of VRRP and STG; the first is optimal and
the second is not.
Planning and Engineering — Network Design
Virtual Router Redundancy Protocol
November 2010 121