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VLAN Configuration Guide

This document summarizes key concepts related to VLANs including: 1. It describes the two main trunk encapsulation standards, 802.1Q and ISL, and their differences in header size, trailer size, standards, and maximum supported VLANs. 2. It defines common VLAN terminology like trunking, native VLAN, access VLAN, voice VLAN, and switched virtual interfaces (SVIs). 3. It explains VLAN configuration options for access ports, trunk ports, and the SVI interface as well as VLAN trunking protocol (VTP) modes and operations.

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424 views1 page

VLAN Configuration Guide

This document summarizes key concepts related to VLANs including: 1. It describes the two main trunk encapsulation standards, 802.1Q and ISL, and their differences in header size, trailer size, standards, and maximum supported VLANs. 2. It defines common VLAN terminology like trunking, native VLAN, access VLAN, voice VLAN, and switched virtual interfaces (SVIs). 3. It explains VLAN configuration options for access ports, trunk ports, and the SVI interface as well as VLAN trunking protocol (VTP) modes and operations.

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opexxx
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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VLANS packetlife.

net

Trunk Encapsulation Trunk Types


Ethernet Header 802.1Q ISL
Header Size 4 bytes 26 bytes
Trailer Size N/A 4 bytes
Standard IEEE Cisco
Maximum VLANs 4096 1000
Command dot1q isl

VLAN Numbers
0 Reserved 1004 fdnet
1 default 1005 trnet
VLAN Creation
1002 fddi-default 1024-4094 Extended
Switch(config)# vlan 100 1003 tr 4095 Reserved
Switch(config-vlan)# name Engineering
Terminology
Access Port Configuration
Trunking · Extending multiple VLANs over the
same physical conenction
Switch(config-if)# switchport mode access
Switch(config-if)# switchport nonegotiate Native VLAN · By default, this VLAN is untagged
Switch(config-if)# switchport access vlan 100
on a trunk
Switch(config-if)# switchport voice vlan 150
Access VLAN · The VLAN to which an access port
Trunk Port Configuration is assigned
Voice VLAN · If configured, enables minimal
Switch(config-if)# switchport mode trunk
trunking to support voice traffic in addition to data
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport trunk allowed vlan 10,100-200 traffic on an access port
Switch(config-if)# switchport trunk native vlan 10
Dynamic Trunking Protocol (DTP) · Can be
used to automatically establish trunks between
SVI Configuration capable ports

Switch(config)# interface vlan100 Switched Virtual Interface (SVI) · A virtual


Switch(config-if)# ip address 192.168.100.1 255.255.255.0 interface which provides a routed gateway into and
out of a VLAN
VLAN Trunking Protocol
Switch Port Modes
Domain · Common to all switches participating in VTP
trunk · Forms an unconditional trunk
Server Mode · Generates and propagates VTP advertisements to
clients; this mode is default on unconfigured switches dynamic desirable · Actively attempts to
neogiate a trunk with the distant end
Client Mode · Receives and forwards advertisements from servers;
VLANs cannot be manually configured on switches in client mode dynamic auto · Will form a trunk only if requested
by the distant end
Transparent Mode · Forwards advertisements but does not
participate in VTP; VLANs must be configured manually access · Will never form a trunk

Pruning · VLANs not having any access ports on an end switch are Troubleshooting
removed from the trunk to reduce flooded traffic
show vlan
VTP Configuration show interface status
Switch(config)# vtp mode server show interface switchport
Switch(config)# vtp domain LASVEGAS
Switch(config)# vtp password Presl3y show interface trunk
Switch(config)# vtp version 2
show vtp status
Switch(config)# vtp pruning
show vtp password

by Jeremy Stretch v1.0

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