Overview; Layer 2 Ethernet Switching Overview; Vlans; Chapter - Cisco Nexus 7000 Series Configuration Manual

Overview

This chapter provides an overview of the Cisco NX-OS devices that support Layer 2 features.
This chapter includes the following sections:
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Layer 2 Ethernet Switching Overview

The device supports simultaneous, parallel connections between Layer 2 Ethernet segments. Switched
connections between Ethernet segments last only for the duration of the packet. New connections can be made
between different segments for the next packet.
The device solves congestion problems caused by high-bandwidth devices and a large number of users by
assigning each device (for example, a server) to its own domain. Because each LAN port connects to a separate
Ethernet collision domain, servers in a switched environment achieve full access to the bandwidth.
Because collisions cause significant congestion in Ethernet networks, an effective solution is full-duplex
communication. Typically, 10/100-Mbps Ethernet operates in half-duplex mode, which means that stations
can either receive or transmit. In full-duplex mode, which is configurable on these interfaces, two stations
can transmit and receive at the same time. When packets can flow in both directions simultaneously, the
effective Ethernet bandwidth doubles. 1/10-Gigabit Ethernet operates in full duplex only.

VLANs

A VLAN is a switched network that is logically segmented by function, project team, or application, without
regard to the physical locations of the users. VLANs have the same attributes as physical LANs, but you can
group end stations even if they are not physically located on the same LAN segment.
Layer 2 Ethernet Switching Overview, page 3
VLANs, page 3
Private VLANs, page 4
Spanning Tree , page 4
Virtualization, page 6
Related Topics, page 7
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x
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