xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch CLI Manual
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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 BPDU 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 4096 element table (defined here as a
vid_range
) which will associate each of the possible 4096 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)
The correct spanning tree priority for the MSTP instance must be entered (
config stp priority
).
c)
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 <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] | fbpdu [enable | disable]}
create stp instance_id
<value 1-4>
config stp instance _id
<value 1-4> [add_vlan | remove_vlan] <vidlist>
delete stp instance_id
<value 1-4>
config stp priority
<value 0-61440> instance_id <value 0-4>
config stp mst_config_id
{revision_level <int 0-65535> | name <string>}
config stp mst_ports
<portlist> instance_id <value 0-4> {internalCost [auto | value 1-200000000] | priority
<value 0-240>}
show stp
show stp ports
{<portlist>}
show stp instance_id
{<value 0-4>}
