Path Cost For Link Aggregate Ports - OmniSwitch os6900 Network Configuration Manual

Configuring STP Port Parameters
configures a 32-bit path cost value for port 1/24 for the flat mode instance to 20,000 (the port speed is 1
GB, 20,000 is the recommended value):
-> spantree cist port 1/24 path-cost 20000
The port path cost value is also configurable for a Multiple Spanning Tree Instance (MSTI). To configure
this value for an MSTI, use the
instance number. For example, the following command configures the path cost value for port
1/12 for MSTI 10 to 19:
-> spantree msti 10 port 1/12 path-cost 19
Note that configuring the port path cost value for a MSTI is allowed in both modes (per-VLAN and flat)
only when the Spanning Tree protocol is set to MSTP.

Path Cost for Link Aggregate Ports

Physical ports that belong to a link aggregate do not participate in the Spanning Tree Algorithm. Instead,
the algorithm is applied to the aggregate logical link (virtual port) that represents a collection of physical
ports. Spanning Tree is automatically enabled on the aggregate logical link and the path cost value is set to
the default value.
If a 32-bit path cost value is in use and the path_cost for a link aggregate is set to zero, the following
default values based on link speed and link aggregate size are used:
Aggregate Size
Link Speed
(number of links)
10 MB
100 MB
1 GB
10 GB
If a 16-bit path cost value is in use and the path_cost for a link aggregate is set to zero, the following
default values based on link speed and link aggregate size are used. Note that for Gigabit ports the aggre-
gate size is not applicable in this case:
Aggregate Size
Link Speed
(number of links)
10 Mbps
page 6-38
spantree msti path-cost
Default Path
Cost Value
2 1,200,000
4 800,000
8 600,000
2 120,000
4 80,000
8 60,000
2 12,000
4 8,000
8 6,000
2 1,200
4 800
8 600
Default Path
Cost Value
2 60
4 40
OmniSwitch AOS Release 7 Network Configuration Guide
Configuring Spanning Tree Parameters
command and specify the MSTI ID for the
June 2013