KB.15.15

Unicast packets with unknown destinations

A meshed switch receiving a unicast packet with an unknown destination does not flood the packet

onto the mesh. Instead, the switch sends a query on the mesh to learn the location of the unicast

destination. The meshed switches then send 802.2 test packets through their non-meshed ports.

After the unicast destination is found and learned by the mesh, subsequent packets having the

same destination address will be forwarded. By increasing the MAC Age Time you can cause

the switch address table to retain device addresses longer. Because the switches in a mesh exchange

address information, this will help to decrease the number of unicast packets with unknown

destinations, which improveslatency within the switch mesh. Also, in an IP environment, HP

Networking recommends that you configure IP addresses on meshed switches. This makes the

discovery mechanism more robust, which contributes to decreased latency. For more on

mac-age-time, see the Basic Operations Guide for your switch.

Spanning tree operation with switch meshing

NOTE: Switch meshing cannot run concurrently with RPVST+.

Using MSTP with several switches and no switch meshing configured can result in unnecessarily

blocking links and reducing available bandwidth. For example:

182 Switch meshing