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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter1 Overview Features
•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 trans ition in g root and
designated ports to the forwarding state
•Optional spanning-tree features available in the PVST+, rapid PVST+, and MSTP modes:
–
Port Fast for eliminating the forwarding delay by enabling a port to immediately transition from
the blocking state to the forwarding state
–
BPDU guard for shutting down Port Fast-enabled ports that receive 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
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Loop guard for preventing alternate or root ports from becoming designated ports beca use of a
failure that leads to a unidirectional link
VLAN Support
•The switches support 250 port-based VLANs for assigning users to VLANs associated with
appropriate network resources, traffic patterns, and bandwidth
Note The Catalyst 2950-12, Catalyst 2950-24, Catalyst 2950SX-24, Catalyst 2950SX-48-SI, and
Catalyst 2950T-48-SI switches support only 64 port-based VLANs.
•The switch supports up to 4094 VLAN IDs to allow service provider networks to suppor t the numb er of
VLANs allowed by the IEEE 802.1Q standard (available only with the EI)
���IEEE 802.1Q trunking protocol on all ports for network moves, adds, and c hanges; management and
control of broadcast and multicast traffic; and network security by establishing VLAN groups for
high-security users and network resources
•VLAN Membership Policy Server (VMPS) for dynamic VLAN membership
•VLAN Trunking Protocol (VTP) pruning for reducing network traffic by restricting flooded traffic
to links destined for stations receiving the traffic
•Dynamic Trunking Protocol (DTP) for negotiating trunking on a link betwee n two d evices and fo r
negotiating the type of trunking encapsulation (802.1Q) to be used
•Voice VLAN for creating subnets for voice traffic from Cisco IP Phones
•VLAN 1 minimization to reduce the risk of spanning-tree loops or storm s by a llowing V LAN 1 to
be disabled on any individual VLAN trunk link. With this feature enabled, no user tra ffic is sent or
received. The switch CPU continues to send and receive control protocol frames.
Security
•Bridge protocol data unit (BPDU) guard for shutting down a Port Fast-c onfigure d por t w he n an
invalid configuration occurs
•Protected port option for restricting the forwarding of traffic to designated ports o n the same switch
•Password-protected access (read-only and read-write access) to management interfaces (CMS and
CLI) for protection against unauthorized configuration changes
•Port security option for limiting and identifying MAC addresses of the stations allowed to access
the port
•Port security aging to set the aging time for secure addresses on a port