NETGEAR S3300-28X (GS728TX) 24x1GE - Инструкция по эксплуатации - Страница 350

 Configuration Examples

350

S3300 Smart Managed Pro Switch 

The difference between the RSTP and the traditional STP (IEEE 802.1D) is the ability to 
configure and recognize full duplex connectivity and ports that are connected to end stations, 
resulting in rapid transitioning of the port to the Forwarding state and the suppression of 
Topology Change Notification. These features are represented by the parameters 

pointtopoint

 and 

edgeport

. MSTP is compatible to both RSTP and STP. It behaves 

appropriately to STP and RSTP bridges.

A MSTP bridge can be configured to behave entirely as a RSTP bridge or a STP bridge. So, 
an IEEE 802.1s bridge inherently also supports IEEE 802.1w and IEEE 802.1D.

The MSTP algorithm and protocol provides simple and full connectivity for frames assigned 
to any given VLAN throughout a Bridged LAN comprising arbitrarily interconnected 
networking devices, each operating MSTP, STP or RSTP. MSTP allows frames assigned to 
different VLANs to follow separate paths, each based on an independent Multiple Spanning 
Tree Instance (MSTI), within Multiple Spanning Tree (MST) Regions composed of LANs and 
or MSTP Bridges. These Regions and the other Bridges and LANs are connected into a 
single Common Spanning Tree (CST). [IEEE DRAFT P802.1s/D13]

MSTP connects all Bridges and LANs with a single Common and Internal Spanning Tree 
(CIST). The CIST supports the automatic determination of each MST region, choosing its 
maximum possible extent. The connectivity calculated for the CIST provides the CST for 
interconnecting these Regions, and an Internal Spanning Tree (IST) within each Region. 
MSTP ensures that frames with a given VLAN ID are assigned to one and only one of the 
MSTIs or the IST within the Region, that the assignment is consistent among all the 
networking devices in the Region and that the stable connectivity of each MSTI and IST at 
the boundary of the Region matches that of the CST. The stable active topology of the 
Bridged 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 via 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. A MSTP bridge will 
transmit 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 which have no Bridges attached that cannot receive 
and transmit MSTP BPDUs. The MST Configuration Identifier has the following components: 

•

Configuration Identifier Format Selector 

•

Configuration Name

•

Configuration Revision Level

•

Configuration Digest: 16-byte signature of type HMAC-MD5 created from the MST 
Configuration Table (a VLAN ID to MSTID mapping)