Spanning tree algorithm, In this chapter, Overview – Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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Chapter
36
Spanning Tree Algorithm
In this chapter
This chapter describes the following basic topics:
•
– Configures detection and response to loopback BPDUs.
•
– Configures global bridge settings for STP, RSTP and MSTP.
•
– Configures interface settings for STA, including priority, path cost,
link type, and designation as an edge port.
•
– Sets the VLANs and associated priority assigned to an MST
instance
•
– Configures interface settings for MSTP, including priority and
path cost.
Overview
The Spanning Tree Algorithm (STA) can be used to detect and disable network loops, and to provide
backup links between switches, bridges or routers. This allows the switch to interact with other
bridging devices (that is, an STA-compliant switch, bridge or router) in your network to ensure that
only one route exists between any two stations on the network, and provide backup links which
automatically take over when a primary link goes down.
The spanning tree algorithms supported by this switch include these versions:
•
STP – Spanning Tree Protocol (IEEE 802.1D)
•
RSTP – Rapid Spanning Tree Protocol (IEEE 802.1w)
•
MSTP – Multiple Spanning Tree Protocol (IEEE 802.1s)
STP – STP uses a distributed algorithm to select a bridging device (STP-compliant switch, bridge or
router) that serves as the root of the spanning tree network. It selects a root port on each bridging
device (except for the root device) which incurs the lowest path cost when forwarding a packet from
that device to the root device. Then it selects a designated bridging device from each LAN which
incurs the lowest path cost when forwarding a packet from that LAN to the root device. All ports
connected to designated bridging devices are assigned as designated ports. After determining the
lowest cost spanning tree, it enables all root ports and designated ports, and disables all other
ports. Network packets are therefore only forwarded between root ports and designated ports,
eliminating any possible network loops.