ZyXEL Communications OLT2406 - Spanning Tree Protocol; Spanning Tree Protocol Overview; What You Can Do; What You Need to Know

OLT2406 User’s Guide
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CHAPTER 14
Spanning Tree Protocol
14.1 Spanning Tree Protocol Overview
The OLT supports Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP) and Multiple
Spanning Tree Protocol (MSTP) as defined in the following standards.
• IEEE 802.1D Spanning Tree Protocol
• IEEE 802.1w Rapid Spanning Tree Protocol
• IEEE 802.1s Multiple Spanning Tree Protocol
The OLT also allows you to set up multiple STP configurations (or trees). Ports can then be assigned to the
trees.
14.1.1 What You Can Do
• Use the Spanning Tree Protocol Status screen (Section 14.2 on page 133) to view the STP status in the
different STP modes (RSTP or MSTP) you can configure on the OLT.
• Use the Spanning Tree Configuration screen (Section 14.3 on page 134) to activate one of the STP
modes on the OLT.
• Use the Rapid Spanning Tree Protocol screen (Section 14.4 on page 134) to configure RSTP settings.
• Use the Rapid Spanning Tree Protocol Status screen (Section 14.5 on page 136) to view the RSTP status.
• Use the Multiple Spanning Tree Protocol screen (Section 14.6 on page 137) to configure MSTP.
• Use the Multiple Spanning Tree Protocol Status screen (Section 14.7 on page 141) to view the MSTP
status.
14.1.2 What You Need to Know
Read on for concepts on STP that can help you configure the screens in this chapter.
(Rapid) Spanning Tree Protocol
(R)STP detects and breaks network loops and provides backup links between switches, bridges or
routers. It allows a switch to interact with other (R)STP -compliant switches in your network to ensure that
only one path exists between any two stations on the network.
The OLT uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allows faster convergence of the
spanning tree than STP (while also being backwards compatible with STP-only aware bridges). In RSTP,
topology change information is directly propagated throughout the network from the device that
generates the topology change. In STP, a longer delay is required as the device that causes a topology
change first notifies the root bridge that then notifies the network. Both RSTP and STP flush unwanted
learned addresses from the filtering database. In RSTP, the port states are Discarding, Learning, and
Forwarding.