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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 1 Overview
Features
Availability Features
• 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 (supported by default on NNIs, can be enabled on ENIs, not supported on UNIs). STP has
these features:
–
Up to 128 supported spanning-tree instances
–
Per-VLAN spanning-tree plus (PVST+) for balancing load across VLANs
–
Rapid PVST+ for balancing load across VLANs and providing rapid convergence of
spanning-tree instances
• IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) on NNIs or ENIs 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
transitioning root and designated port NNIs or spanning-tree enabled ENIs to the forwarding state
• Optional spanning-tree features available in PVST+, rapid-PVST+, and MSTP modes on NNIs and
ENIs where spanning tree has been enabled:
–
Port Fast for eliminating the forwarding delay by enabling a spanning-tree port to immediately
transition from the blocking state to the forwarding state
–
Bridge protocol data unit (BPDU) guard for shutting down Port Fast-enabled ports that receive
BPDUs
–
BPDU filtering for preventing a Port Fast-enabled ports 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 port NNIs or ENIs from becoming designated ports
because of a failure that leads to a unidirectional link
• Flex Link Layer 2 interfaces to back up one another as an alternative to STP for basic link
redundancy in a nonloop network with preemptive switchover and bidirectional fast convergence,
also referred to as the MAC address-table move update feature (requires metro IP access or metro
access image)
• Flex Link Multicast Fast Convergence to reduce the multicast traffic convergence time after a Flex
Link failure
• 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 (requires metro IP access or metro access image)
• Support for Resilient Ethernet Protocol (REP) for improved convergence times and network loop
prevention without the use of spanning tree (requires metro IP access or metro access image)
• Counter and timer enhancements to REP support (requires metro IP access or metro access image)
• HSRP for Layer 3 router redundancy (requires metro IP access image)
• Equal-cost routing for link-level and switch-level redundancy (requires metro IP access image)