Spanning-Tree Address Management; Stp And Ieee 802.1Q Trunks; Spanning Tree And Redundant Connectivity; Figure 6-3 Spanning Tree And Redundant Connectivity - Cisco ONS 15454 Software Feature And Configuration Manual

Spanning-Tree Address Management

Spanning-Tree Address Management

IEEE 802.1D specifies 17 multicast addresses, ranging from 0x00180C2000000 to 0x0180C2000010, to
be used by different bridge protocols. These addresses are static addresses that cannot be removed.
The ML-Series card switches supported BPDUs (0x0180C2000000 and 01000CCCCCCD) when they
are being tunneled via the protocol tunneling feature.

STP and IEEE 802.1Q Trunks

When you connect a Cisco switch to a non-Cisco device through an IEEE 802.1Q trunk, the Cisco switch
uses PVST+ to provide spanning-tree interoperability. PVST+ is automatically enabled on IEEE 802.1Q
trunks after users assign a protocol to a bridge group. The external spanning-tree behavior on access
ports and Inter-Switch Link (ISL) trunk ports is not affected by PVST+.
For more information on IEEE 802.1Q trunks, see

Spanning Tree and Redundant Connectivity

You can create a redundant backbone with spanning tree by connecting two switch interfaces to another
device or to two different devices. Spanning tree automatically disables one interface but enables it if
the other one fails, as shown in
low-speed link is always disabled. If the speeds are the same, the port priority and port ID are added
together, and spanning tree disables the link with the lowest value.
Figure 6-3
You can also create redundant links between switches by using EtherChannel groups. For more
information, see
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
6-8
Figure

Spanning Tree and Redundant Connectivity

Active link
Blocked link
Chapter 9, "Configuring Link Aggregation."
Chapter 7, "Configuring VLANs."
6-3. If one link is high speed and the other is low speed, the
Workstations
Chapter 6 Configuring STP and RSTP
January 2004