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: Spanning tree
- Chapter 10: Layer 3 network design
- Chapter 11: SPBM design guidelines
- Chapter 12: 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
- Multicast for multimedia
- Chapter 13: System and network stability and security
- Chapter 14: QoS design guidelines
- Chapter 15: Layer 1, 2, and 3 design examples
- Chapter 16: Software scaling capabilities
- Chapter 17: Supported standards, RFCs, and MIBs
- Glossary
Chapter 8: Layer 2 loop prevention
This section provides information about how to use bandwidth and network resources efficiently, and to
prevent Layer 2 data loops. Use the information in this section to use loop prevention mechanisms.
Loop prevention and detection
In certain network designs, loops can form. For example, loops can form if you have incorrect
configuration or cabling.
There are two solutions to detect loops: Loop Detect, and Simple Loop Prevention Protocol
(SLPP). Both solutions perform the following functions:
• detect the loop
• automatically stop the loop
• determine on which port the loop is occurring
• shut down the port on which the loop is occurring
Avaya recommends the following loop prevention and recovery features in order of preference:
1. SLPP
2. Loop Detect with ARP-Detect activated
For more information about SLPP and loop detection, see Avaya Virtual Services Platform
4000 Configuration — VLANs and Spanning Tree, NN46251-500.
SLPP
Use SLPP to protect the network against Layer 2 loops. If you configure and enable SLPP, the
switch sends a test packet to the VLAN. A loop is detected if the switch or a peer aggregation
switch on the same VLAN receives the original packet. If the switch detects a loop, the switch
disables the port. After the port is disabled, you must enable the port manually, or use port
auto enable to reenable the port after a predefined interval.
Loops can be introduced into the network in many ways. One way is through the loss of a
multilink trunk configuration caused by user error or malfunction. This scenario does not
introduce a broadcast storm, but because all MAC addresses are learned through the looping
ports, Layer 2 MAC learning is significantly impacted. Spanning tree protocols cannot always
detect such a configuration issue, whereas SLPP reacts and disables the malfunctioning links,
which minimizes the impact on the network.
SLPP configuration considerations and recommendations
SLPP uses an individual VLAN hello packet mechanism to detect network loops. Sending hello
packets on an individual VLAN basis allows SLPP to detect VLAN-based network loops for
Network Design Reference for Avaya VSP 4000 February 2014 43