The collection of bridges in a local area network (LAN) can be depicted as a graph whose nodes are bridges and LAN segments (or cables), and whose edges are the interfaces connecting the bridges to the segments. To break loops in the LAN while maintaining access to all LAN segments, the bridges collectively compute a spanning tree.
For all switches in a network to agree on a loop-free topology, a common frame of reference must exist to use as a guide. This reference point is called the Root Bridge. An election process among all connected switches chooses the Root Bridge. Each switch has a unique Bridge ID.
When a switch first powers up, it assumes that it is the Root Bridge itself. Every switch begins by sending out Bridge Protocol Data Units (BPDUs) with a Root Bridge ID equal to its own Bridge ID and a Sender Bridge ID that is its own Bridge ID. The Sender Bridge ID simply tells other switches who is the actual sender of the BPDU message. After a Root Bridge is decided on, configuration BPDUs are sent only by the Root Bridge. All other bridges must forward or relay the BPDUs, adding their own Sender Bridge IDs to the message.
In earlier releases, IP Manager created VLANs using VLAN IDs. This resulted in duplication of VLAN objects when multiple domains were configured with the same VLAN ID. VLANs were represented as VLAN-<VLAN ID>, for example, VLAN-1003. So the user could not discover all VLAN objects since the topology did not have all the VLAN objects because of VLAN ID duplication.
In this release, IP Manager creates unique VLANs from the Root Bridge ID and VLAN ID, that is, VLAN-<Root Bridge ID>-<VLANID>.
Each VLAN has a different Root Bridge ID because the participating members may be different. From the BRIDGE-MIB, dot1dStpDesignatedRoot (Root Bridge ID) is derived. The dot1dStpDesignatedRoot (OID: 1.3.6.1.2.1.17.2.5) is a combination of dot1dStpPriority (1.3.6.1.2.1.17.2.2 - Value of the write-able portion of the Bridge ID) and dot1dBaseBridgeAddress (The MAC address used by this bridge when it must be referred to in a unique fashion. When concatenated with dot1dStpPriority, a unique BridgeIdentifier is formed which is used in the Spanning Tree Protocol). The combined representation of Root Bridge ID and VLANID in this release is: VLAN-<Root Bridge ID>-<VLANID>.
Depending on the device types, there could be other ID added to the VLAN name, for example:
Alcatel-PR driver - Device name is added after "VLAN" class name:
VLAN-196.36.122.235-00-E0-B1-62-C8-3B-1
VLAN-196.36.122.235-00-E0-B1-62-C8-3B-2
Alcatel-Omni driver - The "Alcatel-Omni" driver is added after the VLAN class name:
VLAN-Alcatel-Omni-00-D0-95-4E-A2-81-1
A new parameter “STPVLANNamingEnabled” is added in the discovery.conf file. STP based VLAN unique naming discovery is enabled by incorporating the root bride ID as part of the VLAN name.
Default Value = TRUE
STPVLANNamingEnabled = TRUE
It is set to TRUE (by default) to enable VLAN unique naming by incorporating STP root bridge ID as part of the VLAN name during IP Manager discovery. If it is set to FALSE, the STP root bridge ID will not be included in the VLAN name.
Here the Root Bridge ID is formed by using only dot1dBaseBridgeAddress (MAC address). The dot1dStpPriority part from dot1dStpDesignatedRoot is not used.
If the Root Bridge ID changes due to network configuration changes, then the SVLAN name needs to be changed too. Any change to the SVLAN name will reflect after performing a "Rediscover All".
For Cisco devices supporting CISCO-VTP-MIB, the combined representation of Root Bridge ID and VLANID is: VLAN-<Root Bridge ID>-<VLANID>[VTP name], for example, VLAN-00-19-AA-CE-1B-00-10[VSAN_NEW].
