INS_CWGE24MS2_REV–
10/05/16 PAGE 185
INSTALLATION AND OPERATION MANUAL
CWGE24MS2
TECH SUPPORT: 1.888.678.9427
Parameter
Description
Hello Time
This is the time interval in seconds between BPDU (Bridge Protocol Data Units)
configuration message generations by the root switch.
Forward Delay
This is the maximum time (in seconds) the Switch will wait before changing states.
This delay is required because every switch must receive information about topology
changes before it starts to forward frames. In addition, each port needs time to listen
for conflicting information that would make it return to a blocking state; otherwise,
temporary data loops might result.
Path Cost
Path cost is the cost of transmitting a frame on to a LAN through that port. It is
recommended to assign this value according to the speed of the bridge. The slower
the media, the higher the cost.
Root Cost
This is the number of the port on the Switch through which this Switch must
communicate with the root of the Spanning Tree.
MSTP
Introduction
MSTP (IEEE 802.1S Multiple STP), which uses RSTP for rapid convergence, enables VLANs to
be grouped into a spanning-tree instance, with each instance having a spanning-tree topology
independent of other spanning-tree instances. This architecture provides multiple forwarding
paths for data traffic, enables load balancing, and reduces the number of spanning-tree instances
required to support a large number of VLANs.
Multiple Spanning-Tree Regions:
For switches to participate in multiple spanning-tree (MST) instances, you must consistently
configure the switches with the same MST configuration information. A collection of
interconnected switches that have the same MST configuration comprises an MST region. The
MST configuration determines to which MST region each switch belongs. The configuration
includes the name of the region, the revision number, and the MST instance-to-VLAN assignment
map. You configure the switch for a region by using the spanning-tree mst configuration global
configuration command, after which the switch enters the MST configuration mode. From
this mode, you can map VLANs to an MST instance by using the instance MST configuration
command, specify the region name by using the name MST configuration command, and set the
revision number by using the revision MST configuration command.
A region can have one member or multiple members with the same MST configuration; each
member must be capable of processing RSTP BPDUs. There is no limit to the number of MST
regions in a network, but each region can support up to 16 spanning-tree instances. You can
assign a VLAN to only one spanning-tree instance at a time.
Boundary Ports
A boundary port is a port that connects an MST region to a single spanning-tree region running
RSTP, or to a single spanning-tree region running 802.1D, or to another MST region with a different
MST configuration. A boundary port also connects to a LAN, the designated switch of which is
either a single spanning-tree switch or a switch with a different MST configuration.
