HP 5400ZL - Manual (Page 140)

Multiple Instance Spanning-Tree Operation
Configuring MSTP
■ 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.)
■ Verify that 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 4­
12.)
■ Identify the edge ports connected to end nodes and enable the admin­
edge-port setting for these ports. Leave the admin-edge-port setting dis­
abled for ports connected to another switch, a bridge, or a hub.
N o t e o n M S T P Under some circumstances the rapid state transitions employed by MSTP can
R a p i d S t a t e increase the rates of frame duplication and misordering in the switched LAN.
Tr a n s i t i o n s To allow MSTP switches to support applications and protocols that may be
sensitive to frame duplication and misordering, setting the Force Protocol
Version (
force-version) parameter to stp-compatible allows MSTP to operate
with rapid transitions disabled. The value of this parameter applies to all ports
on the switch. See the information on
force-version on page 4-23.
4-18