Sample MSTI Configuration
Configuring Spanning Tree Parameters
page 6-50
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
The following commands assign ports 2/1, 5/1, 5/2, and 3/6 to VLANs 100, 150, 200, and 250 on
Switch B:
-> vlan 100 members port 2/1 untagged
-> vlan 150 members port 5/1 untagged
-> vlan 200 members port 5/2 untagged
-> vlan 250 members port 3/6 untagged
5
Create one MSTI using the
command. For example:
-> spantree msti 1
6
Assign VLANs 200 and 250 to MSTI 1. For example:
-> spantree msti 1 vlan 100 200
All VLANs are associated with the CIST instance. As a result, VLANs 100 and 150 do not require any
configuration to map them to the CIST instance.
7
Configure the port path cost (PPC) for all ports on both switches associated with MSTI 1 to a PPC
value that is lower than the PPC value for the ports associated with the CIST instance using the
command. For example, the PPC for ports associated with the CIST instance is set to the
default of 200,000 for 100 MB connections. The following commands change the PPC value for ports
associated with the MSTI 1 to 20,000:
-> spantree msti 1 port 4/8 path-cost 20000
-> spantree msti 1 port 2/12 path-cost 20000
-> spantree msti 1 port 5/2 path-cost 20000
-> spantree msti 1 port 3/6 path-cost 20000
Note.
In this example, port connections between VLANs 150, 200, and 250 are blocked on each switch
initially, as shown in the diagram on
. This is because in flat mode MSTP, each instance is active
on all ports resulting in a comparison of connections independent of VLAN and MSTI associations.
To avoid this and allow VLAN traffic to flow over separate data paths based on MSTI association, Step 7
of this tutorial configures a superior port path cost value for ports associated with MSTI 1. As a result,
MSTI 1 selects one of the data paths between its VLANs as the best path, rather than the CIST data paths,
as shown in the diagram on
.