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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter1 Product Overview
Layer 2 Software Features
•Spanning tree BackboneFast—BackboneFast reduces the time needed f or the spanning tree to
converge after a topology change caused by an indirect link failure. BackboneFast decreases
spanning-tree convergence time for any switch that experiences an indirect link failure.
•Spanning tree root guard—Root guard forces a port to becom e a designated port so that no switch
on the other end of the link can become a root switch.
For information on the STP enhancements, see Chapter 14, “Configuring STP Features.”
SSO
Stateful switchover (SSO) enables you to propagate configuration and state inform ation from the active
to the redundant supervisor engine so that sub-second interruptions in Layer 2 traffic occur when the
active supervisor engine switches over to the redundant supervisor engine.
•Stateful IGMP Snooping
This feature propagates the IGMP data learned by the active supervisor engine to the redundant
supervisor engine so that when a switchover occurs, the newly active supervisor engine is awar e of
the multicast group membership, which alleviates a disruption to multicast traffic during a
switchover.
•Stateful DHCP Snooping
This feature propagates the DHCP-snooped data from the active supervisor engine to the redunda nt
supervisor engine so that when a switchover occurs, the newly active supervisor engine is awar e of
the DHCP data that was already snooped, and the security benefits con tinue uninterrupted.
UBRL
User Based Rate Limiting (UBRL) enables you to adopt microflow policing to dynamically learn traffic
flows and rate limit each unique flow to an individual rate. UBRL is available only on the Supervisor
Engine V-10GE with the built-in NetFlow support.
UDLD
The UniDirectional Link Detection (UDLD) protocol allows devices connected through fiber-optic or
copper Ethernet cables to monitor the physical configuration of the cables and detect a unidirectional
link.
For information about UDLD, see Chapter 20, “Configuring UDLD.”
Unidirectional Ethernet
Unidirectional Ethernet uses only one strand of fiber for either transmitting or receiving one-way traffic
for the Gigaport, instead of two strands of fiber for a full-duplex Gigaport Ethernet.
For information about Unidirectional Ethernet, see Chapter21, “Configuring Unidirectional Ethernet.”