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Catalyst 3750 Metro Switch Software Configuration Guide
78-15870-01
Chapter 1 Overview
Features
• 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 transition 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
VLAN Features
• Support for up to 1005 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
• VLAN Query Protocol (VQP) for dynamic VLAN membership
• Inter-Switch Link (ISL) and IEEE 802.1Q trunking encapsulation on all ports for network moves,
adds, and changes; management and control of broadcast and multicast traffic; and network security
by establishing VLAN groups for high-security users and network resources
• Dynamic Trunking Protocol (DTP) for negotiating trunking on a link between two devices and for
negotiating the type of trunking encapsulation (802.1Q or ISL) to be used
• VLAN Trunking Protocol (VTP) and VTP pruning for reducing network traffic by restricting
flooded traffic to links destined for stations receiving the traffic
• Voice VLAN for creating subnets for voice traffic from Cisco IP Phones
• VLAN 1 minimization for reducing the risk of spanning-tree loops or storms by allowing VLAN 1
to be disabled on any individual VLAN trunk link. With this feature enabled, no user traffic is sent
or received on the trunk, but the switch CPU continues to send and receive control protocol frames.
• VLAN mapping on enhanced-services (ES) ports to translate customer VLANs to service-provider
VLANs for transporting packets across the service-provider network without affecting the customer
VLAN IDs
• Custom ethertype to enable the user to change the ethertype value on a port to any value to direct
the tagged and untagged traffic to different VLANs (ES ports only)
Layer 2 Virtual Private Network (VPN) Services
• 802.1Q tunneling so that customers with users at remote sites across a service-provider network can
keep VLANs segregated from other customers, and Layer 2 protocol tunneling to ensure that the
customer’s network has complete STP, CDP, and VTP information about all users
• Layer 2 protocol tunneling bypass feature to provide interoperability with third-party vendors
• Intelligent 802.1Q tunneling QoS, the ability to copy the inner cost-of-service (CoS) value to the
outer CoS value for 802.1Q tunneling
• Support for Ethernet over multiprotocol layer switching (EoMPLS) tunneling mechanism for
transporting Ethernet frames over a service-provider MPLS network
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