Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 350)

320 Multi-Service IronWare Switching Configuration Guide
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IEEE 802.1D Spanning Tree Protocol (STP)
12
Enabling or disabling STP on a port
Use the following procedure to disable or enable STP on an individual port .
NOTE
If you change the STP state of the primary port in a LAG group, the change affects all ports in the
LAG group.
To enable STP on an individual port, enter commands such as the following.
Brocade(config)# interface 1/1
Brocade(config-if-e1000-1/1)# spanning-tree
Syntax: [no] spanning-tree
STP in a LAG
The STP standard indicates that by default the path cost is determined by link speed. For a1 G port
the path cost is 4 and for 10G port the path cost is 2. However, if a LAG is made consisting of n 1G
ports, where n is less than 10, the path cost remains as 4. The standard does not indicate pathcost
explicitly for LAG interfaces or for bandwidths between standard port bandwidth values, (for
example, between 1G and 10G). Therefore, during STP deployment you may find that though a LAG
has greater bandwidth, its in blocking/discarding state as its pathcost is the same as any 1G link
and the portIndex of 1G port is lower, making the LAG go into a blocking/discarding state. This
behavior is not restricted to 1G or 10G link speed but span across different link speeds. The same
behavior also holds TRUE for RSTP deployments.
Default STP bridge and port parameters
Table 50 lists the default STP bridge parameters. The bridge parameters affect the entire spanning
tree. If you are using MSTP, the parameters affect the VLAN. If you are using SSTP, the parameters
affect all VLANs that are members of the single spanning tree.
NOTE
STP information is specific to a VLAN, and the Multi-Service IronWare software uses the CONTROL
VLAN to get the STP information for the all MIBs under dot1dStp and dot1DStpPortTable. Due to the
limitation of the MIBs, information of per STP implementation of every specific VLAN is not displayed.
TABLE 50 Default STP bridge parameters
Parameter Description Default and valid values
Forward Delay The period of time a bridge will wait (the listen and learn
period) before beginning to forward data packets. 15 seconds
Possible values: 4 – 30 seconds
Maximum Age The interval a bridge will wait for a hello packet from the root
bridge before initiating a topology change. 20 seconds
Possible values: 6 – 40 seconds