DGS-3312SR Layer 3 Gigabit Switch
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10
M
ULTIPLE
S
PANNING
T
REE
P
ROTOCOL
(MSTP) C
OMMANDS
This switch supports three versions of the Spanning Tree Protocol; 802.1d STP, 802.1w Rapid STP and 802.1s MSTP. Multiple
Spanning Tree Protocol, or MSTP, is a standard defined by the IEEE community that allows multiple VLANs to be mapped to a
single spanning tree instance, which will provide multiple pathways across the network. Therefore, these MSTP configurations
will balance the traffic load, preventing wide scale disruptions when a single spanning tree instance fails. This will allow for
faster convergences of new topologies for the failed instance. Frames designated for these VLANs will be processed quickly
and completely throughout interconnected bridges utilizing either of the three spanning tree protocols (STP, RSTP or MSTP).
This protocol will also tag BDPU packets so receiving devices can distinguish spanning tree instances, spanning tree regions
and the VLANs associated with them. These instances will be classified by an
instance_id
. MSTP will connect multiple
spanning trees with a Common and Internal Spanning Tree (CIST). The CIST will automatically determine each MSTP region,
its maximum possible extent and will appear as one virtual bridge that runs a single spanning tree. Consequentially, frames
assigned to different VLANs will follow different data routes within administratively established regions on the network,
continuing to allow simple and full processing of frames, regardless of administrative errors in defining VLANs and their
respective spanning trees. Each switch utilizing the MSTP on a network will have a single MSTP configuration that will have
the following three attributes:
a) A configuration name defined by an alphanumeric string of up to 32 characters (defined in the
config stp mst_config_id
command as
name <string>
).
b) A configuration revision number (named here as a
revision_level
) and;
c) A 4094 element table (defined here as a
vid_range
) which will associate each of the possible 4094 VLANs supported
by the Switch for a given instance.
To utilize the MSTP function on the Switch, three steps need to be taken:
a) The Switch must be set to the MSTP setting (
config stp version
).
b) VLANs that will be shared must be added to the MSTP Instance ID (
config stp instance_id
).
The Multiple Spanning Tree Protocol commands in the Command Line Interface (CLI) are listed (along with the appropriate
parameters) in the following table.
Command Parameters
enable stp
disable stp
config stp version
[mstp | rstp | stp]
config stp
{maxage <value 6-40> | maxhops <value 1-20> | hellotime <value
1-10> | forwarddelay <value 4-30>| txholdcount <value 1-10> |
fbpdu [enable | disable]}
config stp ports
<portlist> {externalCost [auto | <value 1-200000000>] | hellotime
<value 1-10> | migrate [yes | no] | edge [true | false] | p2p [true |
false | auto] | state [enable | disable]
create stp instance_id
<value 1-15>
config stp instance _id <value 1-15> [add_vlan | remove_vlan] <vidlist>
delete stp instance_id
<value 1-15>
config stp priority
<value 0-61440> instance_id <value 0-15>
config stp
{revision_level <int 0-65535> | name <string>}
