Unique VLAN naming
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].