Netgear ‎XS748T-100NES - 48-Port 10G Ethernet Smart Switch

User Manual - Page 365

For XS748T-100NES. Also, The document are for others Netgear models: XS728T, XS748T

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Configuration Examples
365
ProSAFE 10-Gigabit Smart Managed Switch XS728T and XS748T User Manual
LAN with respect to frames consistently classified as belonging to any given VLAN thus
simply and fully connects all LANs and networking devices throughout the network, though
frames belonging to different VLANs can take different paths within any region, per IEEE
DRAFT P802.1s/D13.
All bridges, whether they use STP, RSTP, or MSTP, send information in configuration
messages through Bridge Protocol Data Units (BPDUs) to assign port roles that determine
each port’s participation in a fully and simply connected active topology based on one or
more spanning trees. The information communicated is known as the spanning tree priority
vector. The BPDU structure for each of these different protocols is different. An MSTP bridge
transmits the appropriate BPDU depending on the received type of BPDU from a particular
port.
An MST region comprises of one or more MSTP bridges with the same MST configuration
identifier, using the same MSTIs, and without any bridges attached that cannot receive and
transmit MSTP BPDUs. The MST configuration identifier includes the following components:
1. Configuration identifier format selector
2. Configuration name
3. Configuration revision level
4. Configuration digest: 16-byte signature of type HMAC-MD5 created from the MST
Configuration Table (a VLAN ID to MSTID mapping)
Because multiple instances of spanning tree exist, an MSTP state is maintained on a
per-port, per-instance basis (or on a per-port, per-VLAN basis, as any VLAN can be in one
and only one MSTI or CIST). For example, port A can be forwarding for instance 1 while
discarding for instance 2. The port states changed since IEEE 802.1D specification.
To support multiple spanning trees, configure an MSTP bridge with an unambiguous
assignment of VLAN IDs (VIDs) to spanning trees. For such a configuration, ensure the
following:
1. The allocation of VIDs to filtering identifiers (FIDs) is unambiguous.
2. Each FID that is supported by the bridge is allocated to exactly one spanning tree instance.
The combination of VID to FID and then FID to MSTI allocation defines a mapping of VIDs to
spanning tree instances, represented by the MST Configuration Table.
With this allocation we ensure that every VLAN is assigned to one and only one MSTI. The
CIST is also an instance of spanning tree with an MSTID of 0.
VIDs might be not be allocated to an instance, but every VLAN must be allocated to one of
the other instances of spanning tree.
The portion of the active topology of the network that connects any two bridges in the same
MST region traverses only MST bridges and LANs in that region, and never bridges of any
kind outside the region. In other words, connectivity within the region is independent of
external connectivity.
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