Field
Byte
Description
MST
Configuration
Identifier
51
Indicates the MST configuration identifier, which has
four fields.
CIST Internal
Root Path Cost
4
Indicates the total path costs from the local port to the
IST master. This value is calculated based on link
bandwidth.
CIST Bridge
Identifier
8
Indicates the ID of the designated switching device on
the CIST.
CIST
Remaining
Hops
1
Indicates the remaining hops of the BPDU in the CIST.
MSTI
Configuration
Messages(may
be absent)
16
Indicates an MSTI configuration message. Each MSTI
configuration message occupies 16 bytes. If there are
n
MSTIs, MSTI configuration messages are of
n
x16 bytes.
Configurable MST BPDU Format
Currently, there are two MST BPDU formats:
l
dot1s: BPDU format defined in IEEE 802.1s.
l
legacy: private BPDU format.
If a port transmits either dot1s or legacy BPDUs by default, the user needs to identify the format
of BPDUs sent by the peer, and then runs a command to configure the port to support the peer
BPDU format. Once the configuration is incorrect, a loop probably occurs due to incorrect MSTP
calculation.
By using the
stp compliance
command, you can configure a port on a Huawei datacom device
to automatically adjust the MST BPDU format. With this function, the port automatically adopts
the peer BPDU format. The following MST BPDU formats are supported by Huawei datacom
devices:
l
auto
l
dot1s
l
legacy
In addition to dot1s and legacy formats, the auto mode allows a port to automatically switch to
the BPDU format used by the peer based on BPDUs received from the peer. In this manner, the
two ports use the same BPDU format. In auto mode, a port uses the dot1s BPDU format by
default, and keeps pace with the peer after receiving BPDUs from the peer.
Configurable Maximum Number of BPDUs Sent by a Port at a Hello Interval
BPDUs are sent at Hello intervals to maintain the spanning tree. If a switching device does not
receive any BPDU during a certain period of time, the spanning tree will be re-calculated.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
7 MSTP Configuration
Issue 01 (2014-11-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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