Vrrp And Icmp Redirect Messages - Avaya 8800 Planning And Engineering, Network Design

Layer 3 network design
Figure 41: VRRP and STG configurations
In this figure, configuration A is optimal because VRRP convergence occurs within 2 to 3 seconds.
In configuration A, three STGs are configured and VRRP runs on the link between the two routers
(R). STG 2 is configured on the link between the two routers, which separates the link between the
two routers from the STGs found on the other devices. All uplinks are active.
In configuration B, VRRP convergence takes between 30 and 45 seconds because it depends on
spanning tree convergence. After initial convergence, spanning tree blocks one link (an uplink), so
only one uplink is used. If an error occurs on the uplink, spanning tree reconverges, which can take
up to 45 seconds. After spanning tree reconvergence, VRRP can take a few more seconds to
failover.
Rather than configuring STG with VRRP, Avaya recommends that you enable SMLT with VRRP to
simplify the network configuration and reduce the failover time. For more information about VRRP
and SMLT, see SMLT and Layer 3 traffic Redundant Default Gateway: VRRP

VRRP and ICMP redirect messages

You can use VRRP and Internet Control Message Protocol (ICMP) in conjunction. However, doing
so may not provide optimal network performance.
Consider the network shown in the following figure. Traffic from the client on subnet 30.30.30.0,
destined for the 10.10.10.0 subnet, is sent to routing switch 1 (VRRP Master). This traffic is then
forwarded on the same subnet to routing switch 2 where it is routed to the destination. For each
June 2016 Planning and Engineering — Network Design
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