OmniSwitch os6900 Network Configuration Manual page 134

Configuring STP Bridge Parameters
switches, the new link becomes the root for MSTI 1 and the tagged link between VLAN 2 is blocked, as
shown below:
MSTI-1
If AVC was enabled in the above example, AVC would have assigned the new link an infinite path cost
value that would make this link undesirable as the root for MSTI 1.
Balancing VLANs across links according to their Multiple Spanning Tree Instance (MSTI) grouping is
highly recommended to ensure that there is not a loss of connectivity during any possible topology
changes. Enabling AVC on the switch is another way to prevent undesirable ports from becoming the root
for an MSTI.
To change the default status of the AVC on the switch and to globally enable this feature for all MSTIs,
use the spantree auto-vlan-containment
disable AVC for individual MSTIs using the same command. For example, the following commands
globally enable AVC and then disable it for MSTI 10:
-> spantree auto-vlan-containment enable
-> spantree msti 10 auto-vlan-containment disable
Note. An administratively set port path cost takes precedence and prevents AVC configuration of the path
cost. The exception to this is if the port path cost is administratively set to zero, which resets the path cost
to the default value. In addition, AVC does not have any effect on root bridges.
page 6-32
3/1
VLAN 1
||
4/2
802.1q tag
VLAN 2
command. Once AVC is globally enabled, then it is possible to
OmniSwitch AOS Release 7 Network Configuration Guide
Configuring Spanning Tree Parameters
2/1
VLAN 1
5/1
VLAN 2
MSTI-1
June 2013