User`s guide
Overview of Spanning Tree Protocols
5-2 Configuring Spanning Trees
ThefollowingsectionsdescribethespanningtreeprotocolssupportedbytheMatrixDFESeriesor
N‐SAdevice.
BPDU Bridge Protocol Data Unit messages. Used by STP to exchange information,
including designating a bridge for each switched LAN segment, and one root bridge
for the spanning tree.
Bridge Switching device.
Bridge priority Assigns the bridge’s relative priority compared to other bridges.
CIST Common and Internal Spanning Tree created by MSTP to represent the connectivity
of the entire network. This is equivalent to the single spanning tree used for STP and
RSTP. Communications between MST regions occurs using the CIST.
Designated port A forwarding port within an active topology elected for every switched LAN segment.
Edge port Port on the edge of a bridged LAN.
FID Filter Identifier. Each VLAN is associated to a FID. VLANs are mapped to SIDs using
their FID association.
Forward delay Time interval (in seconds) the bridge spends in listening or learning mode before it
begins forwarding BPDUs.
Hello time Time interval (in seconds) at which the bridge sends BPDUs.
ISLs Inter-Switch Links.
Master port The root port for an entire MST region, providing connectivity from the MST region to
a CIST root that lies outside the MST region.
Max age Maximum time (in seconds) the bridge can wait without receiving a configuration
message (bridge “hello”) before attempting to reconfigure.
MST region An MSTP group of devices configured together to form a logical region. The MST
region presents itself to the rest of the network as a single device, which simplifies
administration.
MSTI Multiple Spanning Tree Instance. Matrix DFE Series and N-SA devices support up to
64 MSTIs.
Path cost Sum of the port costs in a path to a specified destination.
Port cost Value assigned to a port based on the speed of the port. The faster the speed, the
lower the cost. This helps to determine the quickest path between the root bridge
and a specified destination. The segment attached to the root bridge normally has a
path cost of zero.
Port priority Assigns a port’s priority in relation to the other ports on the same bridge.
Root bridge Logical center of the spanning tree, used by STP to determine which paths to block
and which to open.
Root port Port in an active topology through which the root bridge can be reached.
SID Spanning tree identifier. By default, SID 0 is assumed. VLANs are mapped to SIDs
using their FID association.
Table 5-1 Spanning Tree Terms and Definitions (continued)
Term Definition