Design Reference
Table Of Contents
- Contents
- Chapter 1: Introduction
- Chapter 2: New in this release
- Chapter 3: Network design fundamentals
- Chapter 4: Hardware fundamentals and guidelines
- Chapter 5: Optical routing design
- Chapter 6: Platform redundancy
- Chapter 7: Link redundancy
- Chapter 8: Layer 2 loop prevention
- Chapter 9: Layer 2 switch clustering and SMLT
- Chapter 10: Layer 3 switch clustering and RSMLT
- Chapter 11: Layer 3 switch clustering and multicast SMLT
- Chapter 12: Spanning tree
- Chapter 13: Layer 3 network design
- Chapter 14: SPBM design guidelines
- Chapter 15: IP multicast network design
- Multicast and VRF-Lite
- Multicast and MultiLink Trunking considerations
- Multicast scalability design rules
- IP multicast address range restrictions
- Multicast MAC address mapping considerations
- Dynamic multicast configuration changes
- IGMPv3 backward compatibility
- IGMP Layer 2 Querier
- TTL in IP multicast packets
- Multicast MAC filtering
- Guidelines for multicast access policies
- Split-subnet and multicast
- Protocol Independent Multicast-Sparse Mode guidelines
- Protocol Independent Multicast-Source Specific Multicast guidelines
- Multicast for multimedia
- Chapter 16: System and network stability and security
- Chapter 17: QoS design guidelines
- Chapter 18: Layer 1, 2, and 3 design examples
- Glossary
Chapter 12: Spanning tree
Spanning tree prevents loops in switched networks. Avaya Virtual Services Platform 4000 Series
supports Rapid Spanning Tree Protocol (RSTP) and Multiple Spanning Tree Protocol (MSTP). This
chapter describes issues to consider when you configure spanning tree protocols.
For more information about spanning tree protocols, see Configuring VLANs and Spanning Tree on
Avaya Virtual Services Platform 4000 Series, NN46251-500.
Spanning tree and protection against isolated VLANs
Virtual Local Area Network (VLAN) isolation disrupts packet forwarding. The following figure
illustrates the problem. Two VLANs (V1 and V2) connect four devices, and both VLANs are in the
same spanning tree group. V2 includes three of the four devices, whereas V1 includes all four
devices. After a spanning tree protocol detects a loop, it blocks the link with the highest link cost. In
this case, the 100 Mbps link is blocked, which isolates a device in V2. To avoid this problem, either
configure V2 on all four devices or use MSTP with a different Multiple Spanning Tree Instance
(MSTI) for each VLAN.
72 Network Design Reference for Avaya VSP 4000 Series June 2015
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