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Commands for MSTP
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format of the received packets.
Command Mode: Port Mode
Default: Auto Packet Format.
Usage Guide: As the CISCO has adopted the packet format different with the one
provided by IEEE, while many companies also adopted the CISCO format to be CISCO
compatible, we have to provide support to both formats. The standard format is originally
the one provided by IEEE, and the privacy packet format is CISCO compatible. In case
we are not sure about which the packet format is on partner, the AUTO configuration will
be preferred so to identify the format by the packets they sent. The AUTO packet format
is set by default in the concern of better compatibility with previous products and the
leading companies. The packet format will be privacy format before receiving the partner
packet when configured to AUTO.
When the format is not AUTO and the received packet format from the partner does
not match the configured format, we set the state of the port which receives the
unmatched packet to DISCARDING to prevent both sides consider themselves the root
which leads to circuits.
When the AUTO format is set, and over one equipment which is not compatible with
each other are connected on the port (e.g. a equipment running through a HUB or
Transparent Transmission BPDU is connected with several equipments running MSTP),
the format alter counts will be recorded and the port will be disabled at certain count
threshold. The port can only be re-enabled by the administrator.
Example: Configure port message format as the message format of IEEE.
Switch(config)#interface ethernet 1/2
Switch(Config-If-Ethernet1/2)#spanning-tree format standard
Switch(Config-If-Ethernet1/2)#
17.1.12 spanning-tree forward-time
Command: spanning-tree forward-time <time>
no spanning-tree forward-time
Function: Set the switch forward delay time; the command “no spanning-tree
forward-time” restores the default setting.
Parameter: <time> is forward delay time in seconds. The valid range is from 4 to 30.
Command mode: Global Mode
Default: The forward delay time is 15 seconds by default.
Usage Guide: When the network topology changes, the status of the port is changed
from blocking to forwarding. This delay is called the forward delay. The forward delay is