TRENDnet TI-PG1284i User Manual page 130

TRENDnet User's Guide
On a shared boundary link, the MST ports wait in the blocking state for the forward-delay
time to expire before transitioning to the learning state. The MST ports wait another
forward-delay time before transitioning to the forwarding state.

If the boundary port is on a point-to-point link and it is the IST root port, the MST
ports transition to the forwarding state as soon as the IST port transitions to the
forwarding state.

If the IST port is a designated port on a point-to-point link and if the IST port
transitions to the forwarding state because of an agreement received from its peer
port, the MST ports also immediately transition to the forwarding state.

If a boundary port transitions to the forwarding state in an IST instance, it is
forwarding in all MST instances, and a topology change is triggered. If a boundary
port with the IST root or designated port role receives a topology change notice
external to the MST cloud, the MSTP switch triggers a topology change in the IST
instance and in all the MST instances active on that port.
Interoperability with 802.1D STP:
A switch running MSTP supports a built-in protocol migration mechanism that enables it
to interoperate with legacy 802.1D switches. If this switch receives a legacy 802.1D
configuration BPDU (a BPDU with the protocol version set to 0), it sends only 802.1D
BPDUs on that port. An MSTP switch can also detect that a port is at the boundary of a
region when it receives a legacy BPDU, an MSTP BPDU (version 3) associated with a
different region, or an RSTP BPDU (version 2).
However, the switch does not automatically revert to the MSTP mode if it no longer
receives 802.1D BPDUs because it cannot determine whether the legacy switch has been
removed from the link unless the legacy switch is the designated switch. Also, a switch
might continue to assign a boundary role to a port when the switch to which this switch
is connected has joined the region. To restart the protocol migration process (force the
renegotiation with neighboring switches), you can use the clear spanning-tree detected-
protocols privileged EXEC command.
If all the legacy switches on the link are RSTP switches, they can process MSTP BPDUs as
if they are RSTP BPDUs. Therefore, MSTP switches send either a version 0 configuration
and TCN BPDUs or version 3 MSTP BPDUs on a boundary port. A boundary port connects
to a LAN, the designated switch of which is either a single spanning-tree switch or a switch
with a different MST configuration.
© Copyright 2016 TRENDnet. All Rights Reserved.
CLI Configuration
Node Command
enable show spanning-tree
mst configuration
enable show spanning-tree
mst instance
enable show spanning-tree
mst instance <0-63>
enable show spanning-tree
mst instance <0-63>
interface IFNAME
enable show spanning-tree
mst interface IFNAME
enable show spanning-tree
mst root
configure spanning-tree
(disable|enable)
configure spanning-tree mode
mst
configure spanning-tree mst
forward-time
configure no spanning-tree mst
forward-time
configure spanning-tree mst
hello-time
configure no spanning-tree mst
hello-time
TI-PG1284i
Description
This command displays the MSTP
configurations.
This command displays all of the instance
configurations of the MSTP.
This command displays specific instance
configurations of the MSTP.
This command displays specific instance
configurations on an interface of the MSTP.
This command displays the configurations on
an interface of the MSTP.
This command displays the root bridge
configurations.
This command enables / disables the spanning
tree.
This command configures the mode of the
spanning tree. (one of the three modes
STP/RSTP/MSTP.)
This command configures the forward time for
the MSTP.
This command resets the forward time for the
MSTP.
The default forward delay time is 15 seconds.
This command configures the hello time for
the MSTP.
This command resets the hello time for the
MSTP.
The default hello time is 2 seconds.
127