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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Overview
Software Features
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-X 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 on Catalyst
3750-X 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 on Catalyst 3750-X 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 on Catalyst
3750-X 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
• Link-state tracking to mirror the state of the ports that carry upstream traffic from connected hosts
and servers and to allow the failover of the server traffic to an operational link on another Cisco
Ethernet switch
• StackPower redundancy option. You can configure power supplies in a stack in redundant mode so
that an unused power supply will turn on if a power supply in the stack fails.
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