Availability Features; Vlan Features - Cisco 3845 - Security Bundle Router Software Manual

Chapter 1 Overview

Availability Features

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VLAN Features

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OL-23400-01
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 supported spanning-tree instances
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Per-VLAN spanning-tree plus (PVST+) for balancing load across VLANs
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Rapid PVST+ for balancing load across VLANs and providing rapid convergence of
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spanning-tree instances
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 transitioning root and
designated ports to the forwarding state
Optional spanning-tree features available in PVST+, rapid-PVST+, and MSTP modes:
– 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
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Root guard for preventing switches outside the network core from becoming the spanning-tree
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root
Loop guard for preventing alternate or root ports from becoming designated ports because of a
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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
Flex Link Multicast Fast Convergence to reduce the multicast traffic convergence time after a Flex
Link failure
Support for Resilient Ethernet Protocol (REP) for improved convergence times and network loop
prevention without the use of spanning tree
Support for REP edge ports with the no-neighbor option when the neighbor port is not REP-capable
HSRP for Layer 3 router redundancy
Equal-cost routing for link-level and switch-level redundancy (requires metro IP access image)
Support for up to 4094 VLANs for assigning users to VLANs associated with appropriate network
resources, traffic patterns, and bandwidth
Support for VLAN IDs in the full 1 to 4094 range allowed by the IEEE 802.1Q standard
Cisco ME 3800X and 3600X Switch Software Configuration Guide
Features
1-5