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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 1 Product Overview
Layer 2 Software Features
• Per-VLAN Rapid Spanning Tree, page 1-8
• Quality of Service, page 1-9
• Resilient Ethernet Protocol, page 1-10
• SmartPort Macros, page 1-10
• Spanning Tree Protocol, page 1-10
• Stateful Switchover, page 1-10
• SVI Autostate, page 1-11
• Unidirectional Link Detection, page 1-11
• VLANs, page 1-11
• Virtual Switching Systems (Catalyst 4500-X and Supervisor Engine 7-E, 7L-E, and 8-E), page 1-12
• Virtual Switch System Client, page 1-12
• Y.1731 (AIS and RDI), page 1-13
802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
802.1Q tunneling is a Q-in-Q technique that expands the VLAN space by retagging the tagged packets
that enter the service provider infrastructure. 802.1Q tunneling allows service providers to assign a
VLAN to each customer without losing the original customer VLAN IDs inside the tunnel. All data
traffic that enters the tunnel is encapsulated with the tunnel VLAN ID. Layer 2 Protocol Tunneling is a
similar technique for all Layer 2 control traffic.
To map customer VLANs to service-provider VLANs, you can configure VLAN mapping (or VLAN ID
translation) on trunk ports connected to a customer network. Packets entering the port are mapped to a
service provider VLAN (S-VLAN) based on the port number and the original customer VLAN-ID
(C-VLAN) of the packet.
For information on configuring 802.1Q tunneling and VLAN Mapping, see Chapter 30, “Configuring
802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling.”
Cisco IOS Auto Smartport Macros
Cisco IOS Auto SmartPort macros dynamically configure ports based on the device type detected on the
port. When the switch detects a new device on a port it applies the appropriate Cisco IOS Auto
Smartports macro. When a link-down event occurs on the port, the switch removes the macro. For
example, when you connect a Cisco IP phone to a port, Cisco IOS Auto SmartPorts automatically applies
the IP phone macro. The IP phone macro enables quality of service (QoS), security features, and a
dedicated voice VLAN to ensure proper treatment of delay-sensitive voice traffic.
For information on configuring SmartPort macros, see Chapter 22, “Configuring Cisco IOS Auto
Smartport Macros.”
Cisco Discovery Protocol
The Cisco Discovery Protocol (CDP) is a device-discovery protocol that is both media- and
protocol-independent. CDP is available on all Cisco products, including routers, switches, bridges, and
access servers. Using CDP, a device can advertise its existence to other devices and receive information
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