Cisco Systems 3750E manual Availability and Redundancy Features

Chapter 1 Overview

Features

Availability and Redundancy Features

These are the availability and redundancy features:

•HSRP for command switch and Layer 3 router redundancy

•Automatic stack master re-election (failover support) for replacing stack masters that become unavailable only on Catalyst 3750-E switches

The newly elected stack master begins accepting Layer 2 traffic in less than 1 second and Layer 3 traffic between 3 to 5 seconds.

•Cross-stack EtherChannel for providing redundant links across the switch stack (only Catalyst 3750-E switches)

•UniDirectional Link Detection (UDLD) and aggressive UDLD for detecting and disabling unidirectional links on fiber-optic interfaces caused by incorrect fiber-optic wiring or port faults

•IEEE 802.1D Spanning Tree Protocol (STP) for redundant backbone connections and loop-free networks. STP has these features:

–Up to 128 spanning-tree instances supported

–Per-VLAN spanning-tree plus (PVST+) for load-balancing across VLANs

–Rapid PVST+ for load-balancing across VLANs and providing rapid convergence of spanning-tree instances

–UplinkFast, cross-stack UplinkFast (only Catalyst 3750-E switches), and BackboneFast for fast convergence after a spanning-tree topology change and for achieving load-balancing between redundant uplinks, including Gigabit uplinks and cross-stack Gigabit uplinks (only Catalyst 3750-E switches)

•IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) for grouping VLANs into a spanning-tree instance and for providing multiple forwarding paths for data traffic and load-balancing and rapid per-VLAN Spanning-Tree plus (rapid-PVST+) based on the IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) for rapid convergence of the spanning tree by immediately changing root and designated ports to the forwarding state

•Optional spanning-tree features available in PVST+, rapid-PVST+, and MSTP mode:

–Port Fast for eliminating the forwarding delay by enabling a port to immediately change from the blocking state to the forwarding state

–BPDU guard for shutting down Port Fast-enabled ports that receive bridge protocol data units (BPDUs)

–BPDU filtering for preventing a Port Fast-enabled port from sending or receiving BPDUs

–Root guard for preventing switches outside the network core from becoming the spanning-tree root

–Loop guard for preventing alternate or root ports from becoming designated ports because of a failure that leads to a unidirectional link

•Equal-cost routing for link-level and switch-level redundancy

•Flex Link Layer 2 interfaces to back up one another as an alternative to STP for basic link redundancy

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 1-7