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Fig. 8.23, Cst and ist of mstp (2) – Siemens S223 User Manual

Page 211

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User Manual UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

A50010-Y3-C150-2-7619 211

In CST, A and B are the switches operating with STP and C, D and, E are those operating
with MSTP. First, in CST, CIST is established to decide CST Root. After CST root is de-
cided, the closest switch to CST root is decided as IST root of the region. Here, CST root
in IST is IST root.

Legacy 802.1d

CST Root & IST Root

Switch A

Switch D

Switch C

Switch E

Instance 2

Instance 3

Instance 2

Instance 1

Region B (IST)

IST Root

CST

Switch B

IST Root

Region A (IST)

Region C (IST)

Fig. 8.23

CST and IST of MSTP (2)

In above situation, if B operates with MSTP, B will send it’s BPDU to CST root and IST
root in order to request itself to be CST root. However, if any BPDU having higher priority
than that of B is sent, B cannot be CST root.

For the hiD 6615 S223/S323, the commands configuring MSTP are also used to config-
ure STP and RSTP.

8.3.4 Configuring

STP/RSTP/MSTP/PVSTP/PVRSTP Mode (Required)

First of all, you need to configure force-version to decide the mode before STP is config-
ured. To decide force-version of the switch, use the following command.

Command Mode

Description

stp force-version

{stp | rstp |

mstp

| pvstp | pvrstp}

Bridge

Configures Force-version in the bridge.

To delete STP configuration from the switch, use the following command.

Command Mode

Description

no stp force-version

Bridge

Removes force-version configuration.

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