Multi-Instance Spanning Tree And Vlans; Spanning-Tree Parameters - Cisco ONS 15327 User Documentation

Chapter 9 Ethernet Operation
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
Display the CTC card view.
Step 1
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.
Click Apply.
Step 4

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
Parameter
BridgeID
TopoAge
TopoChanges
DesignatedRoot
RootCost
RootPort
MaxAge
June 2002
Spanning-Tree Parameters
Description
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.
Amount of time in seconds since the last topology change.
Number of times the spanning-tree topology has been changed since the node
booted up.
Designated root of the spanning tree for a particular spanning-tree instance.
Total path cost to the designated root.
Port used to reach the root.
Maximum time that received protocol information is retained before it is discarded.
Spanning Tree (IEEE 802.1D)
Cisco ONS 15327 User Documentation, R3.3
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