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Cisco ONS 15327 User Documentation, R3.3
June 2002
Chapter 9 Ethernet Operation
Spanning Tree (IEEE 802.1D)
To remove loops, STP defines a tree that spans all the switches in an extended network. STP forces
certain redundant data paths into a standby (blocked) state. If one network segment in the STP becomes
unreachable, the spanning-tree algorithm reconfigures the spanning-tree topology and reactivates the
blocked path to reestablish the link. STP operation is transparent to end stations, which do not
discriminate between connections to a single LAN segment or to a switched LAN with multiple
segments. The ONS 15327 supports one STP instance per circuit and a maximum of eight STP instances
per ONS 15327.
9.6.1 Multi-Instance Spanning Tree and VLANs
The ONS 15327 can operate multiple instances of STP to support VLANs in a looped topology. You can
dedicate separate circuits across the SONET ring for different VLAN groups (i.e., one for private TLS
services and one for Internet access). Each circuit runs its own STP to maintain VLAN connectivity in
a multi-ring environment.
Procedure: Enable Spanning Tree on Ethernet Ports
Step 1
Display the CTC card view.
Step 2
Click the
Provisioning > Port
tabs.
Step 3
In the left column, find the applicable port number and check the
Stp
Enabled
check box to enable STP
for that port.
Step 4
Click
Apply
.
9.6.2 Spanning-Tree Parameters
Default spanning tree parameters are appropriate for most situations. Contact the Cisco Technical
Assistance Center (TAC) at 1-877-323-7368 before
you change the default STP parameters.
At the node view, click the
Maintenance
>
Etherbridge > Spanning Trees
tabs to view spanning tree
parameters.
Table 9-5
Spanning-Tree Parameters
Parameter Description
BridgeID
ONS 15327 unique identifier that transmits the configuration bridge protocol data
unit (BPDU); the bridge ID is a combination of the bridge priority and the ONS
15327 MAC address.
TopoAge
Amount of time in seconds since the last topology change.
TopoChanges
Number of times the spanning-tree topology has been changed since the node
booted up.
DesignatedRoot
Designated root of the spanning tree for a particular spanning-tree instance.
RootCost
Total path cost to the designated root.
RootPort
Port used to reach the root.
MaxAge
Maximum time that received protocol information is retained before it is discarded.
Содержание ONS 15327
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Страница 82: ...1 32 Cisco ONS 15327 User Documentation R3 3 June 2002 Chapter 1 Hardware Installation Hardware Specifications ...
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