KB.15.15

conservative approach when designing new mesh implementations is to use the two-tier design

and limit the mesh domain to eight switches where possible.

Example 144 A two-tier mesh design

Example 145 A fully interconnected mesh with the maximum switch count

Other factors affecting the performance of mesh networks include the number of destination

addresses that have to be maintained, and the overall traffic levels and patterns. However, a

conservative approach when designing new mesh implementations is to use the two-tier design

and limit the mesh domain to eight switches where possible.

Configuring VRRP with concurrent meshing and routing

See the Multicast and Routing Guide for your switch.

• The VRRP configuration parameter preempt-delay-time should be set to at least 60 for

each virtual router. This is because meshing is a distributed protocol that takes some time to

stabilize when a new switch enters the mesh. A failing switch will be treated as new when it

reenters the mesh. Since meshing is an L2 protocol, it must be stable before L3 VRRP can

become active. The preempt-delay-time is only observed in the case where an already active

VRRP router exists. This will allow the existing router to continue serving its role until the

preferred router, owner or higher priority backup, is truly ready to take over.

• The VRRP configuration parameter nonstop will not be configurable when VRRP is configured

within a mesh. This is because the VRRP nonstop configuration attempts to make VRRP hitless

in the case of a failed management module. Meshing, however, is not hitless in this case.

Having the nonstop parameter set will cause the VRRP virtual router to ignore the

preempt-delay-time and will have the virtual router attempt to become active before

meshing is ready. This will result in a potential 30 or more second routed traffic gap while

meshing becomes stable.

• For best network resiliency during a VRRP failover event, all switches in the mesh domain must

be running x.15.09 or later version of the switch software. This is because changes in versions

186 Switch meshing