Tips For Planning An Mstp Application - HP ProCurve Series 2810 Management And Configuration Manual

Multiple Instance Spanning-Tree Operation
802.1s Multiple Spanning Tree Protocol (MSTP)
5-16
incompatibility between devices running the older 802.1D STP and your
switch running MSTP or RSTP. Please see the "Note on Path Cost" on page 5-5
for more information on adjusting to this incompatibility.

Tips for Planning an MSTP Application

■ Ensure that the VLAN configuration in your network supports all of the
forwarding paths necessary for the desired connectivity. All ports con-
necting one switch to another within a region and one switch to another
between regions should be configured as members of all VLANs config-
ured in the region.
■ All ports or trunks connecting one switch to another within a region
should be configured as members of all VLANs in the region. Otherwise,
some VLANs could be blocked from access to the spanning-tree root for
an instance or for the region.
■ Plan individual regions based on VLAN groupings. That is, plan on all
MSTP switches in a given region supporting the same set of VLANs. Within
each region, determine the VLAN membership for each spanning-tree
instance. (Each instance represents a single forwarding path for all VLANs
in that instance.)
■ There is one logical spanning-tree path through the following:
• Any inter-regional links
• Any IST or MST instance within a region
• Any legacy (802.1D or 802.1w) switch or group of switches. (Where
multiple paths exist between an MST region and a legacy switch,
expect the CST to block all but one such path.)
■ Determine the root bridge and root port for each instance.
Determine the designated bridge and designated port for each LAN seg-
■
ment.
■ Determine which VLANs to assign to each instance, and use port trunks
with 802.1Q VLAN tagging where separate links for separate VLANs would
result in a blocked link preventing communication between nodes on the
same VLAN. (Refer to "MSTP Operation with 802.1Q VLANs" on page
5-11.)
Identify the edge ports connected to end nodes and enable the
■
admin-edge-port setting for these ports. Leave the admin-edge-port setting
disabled for ports connected to another switch, a bridge, or a hub.