Spanning Tree Implementations In Trunk Groups; Multiple Spanning Trees - Radware Alteon Application Manual

Alteon Application Switch Operating System Application Guide
Spanning Tree Protocol
Removing a Port
When you remove a port from a VLAN that belongs to an STG, that port will also be removed from
the STG. However, if that port belongs to another VLAN in the same STG, the port remains in the
STG.
Example
Port 1 belongs to VLAN1, and VLAN1 belongs to STG1. When you remove port 1 from VLAN1, port 1
is also removed from STG1.
However, if port 1 belongs to both VLAN1 and VLAN2 and both VLANs belong to STG1, removing port
1 from VLAN1 does not remove port 1 from STG1 because VLAN2 is still a member of STG1.
Disabling an STG
An STG cannot be deleted, only disabled. If you disable the STG while it still contains VLAN
members, STP will be off on all ports belonging to that VLAN.

Spanning Tree Implementations in Trunk Groups

In both Cisco and Alteon spanning tree implementations as described in Spanning Tree Group
Configuration Guidelines, page 100, the trunking methodology applies to both the default and non-
default STGs. Make sure that all members of the trunk group are configured to the correct STG
parameters, and determine whether to enable use of the Alteon multiple STG mode.
Caution: All ports that are within a trunk group should be configured to have the same spanning
tree and VLAN parameters. Spanning tree parameters should not be changed on individual ports
that belong to a trunk group. To change spanning tree parameters on one or more ports belonging
to a trunk group, first remove individual members from the trunk group.

Multiple Spanning Trees

Alteon supports the Multiple Spanning Tree Protocol (MSTP) and Rapid Spanning Tree Protocol
(RSTP) as defined in the IEEE 802.1S (MSTP) and 802.1W (RSTP) standards. This is an
improvement over previous spanning tree implementations in that it is a standards-based approach
to implementing this functionality.
Before the 802.1S standard, MSTP was implemented through a variety of proprietary protocols such
as Alteon MSTP and Cisco PVST+. Each one of these proprietary protocols had advantages and
disadvantages but they were never interoperable. The 801.S standard solves this by creating
standards-based MSTP. The 802.1W standard takes the same approach in creating standards-based
RSTP.
In this implementation of MSTP, up to 2048 VLANs can be mapped to any of the 16 spanning tree
instances. Each spanning tree instance handles multiple VLANs that have the same Layer 2 topology
but each spanning tree instance can have a topology independent of other instances. Also, MSTP
provides multiple forwarding paths for data traffic, enables load balancing, and improves overall
network fault tolerance.
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Document ID: RDWR-ALOS-V2900_AG1302