HP 6120XG HP ProCurve Series 6120 Blade Switches Advanced Traffic Management G - Page 122

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 segment. ■ 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 412.) ■ Identify the edge ports connected to end nodes and enable the adminedge-port setting for these ports. Leave the admin-edge-port setting disabled for ports connected to another switch, a bridge, or a hub. Note on MSTP Rapid State Tr a n s i t i o n s Under some circumstances the rapid state transitions employed by MSTP can increase the rates of frame duplication and misordering in the switched LAN. 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 4-22. 4-18