Dell Force10 Z9000 FTOS Configuration Guide for Z9000 System - Page 595

Influence MSTP Root Selection MSTP determines the root bridge, but you can assign one bridge a lower priority to increase the probability that it will become the root bridge. To change the bridge priority: Task Assign a number as the bridge priority. A lower number increases the probability that the bridge becomes the root bridge. Range: 0-61440, in increments of 4096 Default: 32768 Command Syntax msti instance bridge-priority priority Command Mode PROTOCOL MSTP The simple configuration Figure 27-1 by default yields the same forwarding path for both MSTIs. Figure 27-5, shows how R3 is assigned bridge priority 0 for MSTI 2, which elects a different root bridge than MSTI 2. View the bridge priority using the command show config from PROTOCOL MSTP mode, also shown in Figure 27-5. Figure 27-5. Changing the Bridge Priority R3(conf-mstp)#msti 2 bridge-priority 0 1d2h51m: %RPM0-P:RP2 %SPANMGR-5-STP_ROOT_CHANGE: MSTP root changed for instance 2. My Bridge ID: 0:0001.e809.c24a Old Root: 32768:0001.e806.953e New Root: 0:0001.e809.c24a R3(conf-mstp)#show config ! protocol spanning-tree mstp no disable MSTI 1 VLAN 100 MSTI 2 VLAN 200,300 MSTI 2 bridge-priority 0 Interoperate with Non-FTOS Bridges FTOS supports only one MSTP region. A region is a combination of three unique qualities: • Name is a mnemonic string you assign to the region. The default region name on FTOS is null. • Revision is a two-byte number. The default revision number on FTOS is 0. • VLAN-to-instance mapping is the placement of a VLAN in an MSTI. For a bridge to be in the same MSTP region as another, all three of these qualities must match exactly. The default values for name and revision will match on all Dell Force10 FTOS equipment. If you have non-FTOS equipment that will participate in MSTP, ensure these values to match on all the equipment. Note: Some non-FTOS equipment may implement a non-null default region name. SFTOS, for example, uses the Bridge ID, while others may use a MAC address. Multiple Spanning Tree Protocol (MSTP) | 595