Stp Per Vlan Group - HP 9304m Installation And Getting Started Manual

Installation and Getting Started Guide
HP9300(config-vlan-10)# no super-span
Syntax: [no] super-span

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 only 128 instances of standard STP on an HP 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 6.7 shows an example of a STP per VLAN group implementation.
Figure 6.7 STP per VLAN Group Example
Member
VLAN 3
Member
VLAN 4
Member
VLAN 13
Member
VLAN 14
A master VLAN contains one or more member VLANs. Each of the member VLANs in a master VLAN runs the
same instance of STP and uses the STP parameters configured for the master VLAN. In this example, the HP
device 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 ports in the VLANs 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's spanning tree are used by another STP group's spanning
tree for forwarding. See "Configuration Example for STP Load Sharing" on page 6-36 for an example using STP
load sharing.
Configuring STP per VLAN Group
To configure STP per VLAN group:
• Configure the member VLANs.
6 - 34
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