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DGS-3312SR
Инструкция по эксплуатации Страница: 84

D-Link DGS-3312SR [84/290] D 802 w 802 s compa

DGS-3312SR Stackable Gigabit Layer 3 Switch

transition states disabled, blocking and listening used in 802.1d and creates a single state Discarding. In either case, ports

do not forward packets. In the STP port transition states disabled, blocking or listening or in the RSTP/MSTP port state

discarding, there is no functional difference, the port is not active in the network topology. Table 6-1 below compares how

the three protocols differ regarding the port state transition.

All three protocols calculate a stable topology in the same way. Every segment will have a single path to the root bridge.

All bridges listen for BPDU packets. However, BPDU packets are sent more frequently - with every Hello packet. BPDU

packets are sent even if a BPDU packet was not received. Therefore, each link between bridges is sensitive to the status of

the link. Ultimately this difference results in faster detection of failed links, and thus faster topology adjustment. A draw-

back of 802.1d is this absence of immediate feedback from adjacent bridges.

802.1d MSTP 802.1w RSTP 802.1d STP Forwarding Learning

Discarding D No iscarding Disabled No

Discarding Discarding Blocking No No

Discarding Discarding Listening No No

Learning Learning Learning No Yes

Forwarding Forwarding Forwarding Yes Yes

Table 4- 1. Comparing Port States

RSTP is capable of a more rapid trans

compliant bridges are sensitive to feedb s. Ports do not need to wait for the

topology to stabilize before transitioning to a forwarding state. In order to allow this rapid transition, the protocol

ariables:

Edge Port

used for a port that is directly connected to a segment where a loop cannot be

mmediately becoming a normal spanning tree port.

P2P Port

A P2P port is also capable of r idges. Under RSTP/MSTP, all

nually overridden through configuration.

tibility

STP can interop cally adjusting BPDU packets to 802.1d

when necessary. Ho

change detection o

legacy equipment on a segm r MSTP.

The Spanning Tree Protocol (ST ope

1. On the Switch level, the settin

2. On the port level, the settings of ports basis.

ition to a forwarding state - it no longer relies on timer configurations - RSTP

ack from other RSTP compliant bridge link

introduces two new v the edge port and the point-to-point (P2P) port.

The edge port is a configurable designation

created. An example would be a port connected directly to a single workstation. Ports that are designated as edge ports

transition to a forwarding state immediately without going through the listening and learning states. An edge port loses its

status if it receives a BPDU packet, i

apid transition. P2P ports may be used to connect to other br

ports operating in full-duplex mode are considered to be P2P ports, unless ma

802.1d / 802.1w / 802.1s Compa

MSTP or R erate with legacy equipment and is capable of automati

format

topology

wever, any segment using 802.1d STP will not benefit from the rapid transition and rapid

f MSTP or RSTP. The protocol also provides for a variable used for migration in the event that

ent is updated to use RSTP o

P) rates on two levels:

gs are globally implemented.

are implemented on a per user-defined group

D-Link DGS-3312SR [84/290] D 802 w 802 s compa

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