Quick Reference Guide

VLAN Commands 791
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VLAN Commands
Dell Networking N2000/N3000/N4000 Series Switches
Dell Networking 802.1Q VLANs are an implementation of the Virtual Local
Area Network, specification 802.1Q. Operating at Layer 2 of the OSI model,
the VLAN is a means of parsing a single network into logical user groups or
organizations as if they physically resided on a dedicated LAN segment of
their own. In reality, this virtually defined community may have individual
members scattered across a large, extended LAN. The VLAN identifier is part
of the 802.1Q tag, which is added to an Ethernet frame by an 802.1Q-
compliant switch or router. Devices recognizing 802.1Q-tagged frames
maintain appropriate tables to track VLANs. The first 3 bits of the 802.1Q tag
are used by 802.1p to establish priority for the packet.
Dell Networking switches supports 802.1Q VLANs. As such, ports may
simultaneously belong to multiple VLANs. VLANs allow a network to be
logically segmented without regard to the physical locations of devices in the
network.
Dell Networking switches supports up to 4093 VLANs for forwarding.
Interfaces can be configured in trunk mode (multiple VLAN support) or
access mode (single VLAN support).
VLANs can be allocated by subnet and netmask pairs, thus allowing
overlapping subnets. For example, subnet 10.10.128.0 with Mask
255.255.128.0 and subnet 10.10.0.0 with Mask 255.255.0.0 can have different
VLAN associations.
Double VLAN Mode
An incoming frame is identified as tagged or untagged based on Tag Protocol
Identifier (TPID) value it contains. The 802.1Q standard specifies a TPID
value (0x8100) to recognize an incoming frame as tagged or untagged. Any
valid Ethernet frame with a value 0x8100 in the 12th and 13th bytes is
recognized as tagged frame. 802.1Q switches check the 12th and 13th bytes to
decide the tag status of incoming frame.
2CSNXXX_SWUM200.book Page 791 Tuesday, December 10, 2013 1:22 PM