Stp load balancing, Configuring stp per vlan group – Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide User Manual
Page 314
FIGURE 65 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).
STP load balancing
Notice that the STP groups each have different STP priorities. In configurations that use the STP
groups on multiple devices, you can use the STP priorities to load balance the STP traffic. By setting
the STP priorities for the same STP group to different values on each device, you can cause each of
the devices to be the root bridge for a different STP group. This type of configuration distributes the
traffic evenly across the devices and also ensures that ports that are blocked in one STP group
spanning tree are used by another STP group spanning tree for forwarding. Refer to
on page 315 for an example using STP load sharing.
Configuring STP per VLAN group
To configure STP per VLAN group, perform the following tasks:
1. Configure the member VLANs.
2. Optionally, configure master VLANs to contain the member VLANs. This is useful when you have a
lot of member VLANs and you do not want to individually configure STP on each one. Each of the
member VLANs in the STP group uses the STP settings of the master VLAN.
3. Configure the STP groups. Each STP group runs a separate instance of STP.
The following CLI commands implement the STP per VLAN group configuration shown in
on page 314. The following commands configure the member VLANs (3, 4, 13, and 14) and the
master VLANs (2 and 12). Notice that changes to STP parameters are made in the master VLANs
only, not in the member VLANs.
device(config)#vlan 2
device(config-vlan-2)#spanning-tree priority 1
device(config-vlan-2)#tagged ethernet 1/1 to 1/4
STP load balancing
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FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide
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