Configuration Guide User guide

FastIron Configuration Guide 1153
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STP feature configuration
The detail parameter and its additional optional parameters display detailed information for
individual ports. Refer to “Displaying detailed STP information for each interface” on page 1099.
STP per VLAN group
STP per VLAN group is an STP enhancement that provides scalability while overcoming the
limitations of the following scalability alternatives:
• Standard STP – You can configure up to 254 instances of standard STP on a Brocade device. It
is possible to need more instances of STP than this in large configurations. Using STP per
VLAN group, you can aggregate STP instances.
• Single STP – Single STP allows all the VLANs to run STP, but each VLAN runs the same instance
of STP, resulting in numerous blocked ports that do not pass any Layer 2 traffic. STP per VLAN
group uses all available links by load balancing traffic for different instances of STP on
different ports. A port that blocks traffic for one spanning tree forwards traffic for another
spanning tree.
STP per VLAN group allows you to group VLANs and apply the same STP parameter settings to all
the VLANs in the group. Figure 151 shows an example of a STP per VLAN group implementation.
FIGURE 151 STP per VLAN group example
A master VLAN contains one or more member VLANs. Each of the member VLANs in the STP Group
runs the same instance of STP and uses the STP parameters configured for the master VLAN. In
this example, the FastIron switch is configured with VLANs 3, 4, 13, and 14. VLANs 3 and 4 are
grouped in master VLAN 2, which is in STP group 1. VLANs 13 and 14 are grouped in master VLAN
12, which is in STP group 2. The VLANs in STP group 1 all share the same spanning tree. The
VLANs in STP group 2 share a different spanning tree.
All the portss are tagged. The ports must be tagged so that they can be in both a member VLAN
and the member's master VLAN. For example, ports 1/1 – 1/4 are in member VLAN 3 and also in
master VLAN 2 (since master VLAN 2 contains member VLAN 3).
Member
VLAN 3
Member
VLAN 4
Member
VLAN 13
Member
VLAN 14
STP group 1
Master VLAN 2
Member VLAN 3
Member VLAN 4
STP priority 1
STP group 2
Master VLAN 12
Member VLAN 13
Member VLAN 14
STP priority 2
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