Creation Of An Ethernet Vlan - Cisco Catalyst 2000 Configuration Handbook

88 Cisco LAN Switching Configuration Handbook

Creation of an Ethernet VLAN

VLANs are created on Layer 2 switches to control broadcasts and enforce the use of a
Layer 3 device for communications. Each VLAN is created in the local switch's database
for use. If a VLAN is not known to a switch, that switch cannot transfer traffic across
any of its ports for that VLAN. VLANs are created by number, and there are two ranges
of usable VLAN numbers (normal range 1 to 1000 and extended range 1025 to 4096).
When a VLAN is created, you can also give it certain attributes such as a VLAN name,
VLAN type, and its operational state. To create a VLAN, use the following steps.
Configure VTP.
1.
VTP is a protocol used by Cisco switches to maintain a consistent database between
switches for trunking purposes. VTP is not required to create VLANs; however,
Cisco has set it up to act as a conduit for VLAN configuration between switches as a
default to make administration of VLANs easier. Because of this, you must first
either configure a VTP with a domain name or disable VTP on the switch. VTP is
explained in detail in section "6-4: VLAN Trunking Protocol."
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(global) vtp domain domain-name
By default, the VTP is in server mode and must be configured with a domain name
before any VLANs can be created. These commands specify the VTP domain name.
OR
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(global) vtp mode transparent
Another option is to disable VTP synchronization of the databases. Disabling it
enables you to manage your local VTP database without configuring and relying on
VTP. You can configure the VTP parameters in global configuration mode as well.
Create the VLAN.
2.
VLANs are created by number. The two ranges of VLANs are as follows:
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Extended VLANs are supported in switches running IOS software. When you create
a VLAN, you have many options to consider, several of which are valid only for
FDDI and Token Ring VLANs. Some of the items configured deal with options, such
as private VLANs, which are discussed in other sections in this book. VLANs are
created using the vlan command in global mode. For Ethernet VLANs, you can also
configure the standard parameters, as shown in Table 6-1.
Specify a VTP name:
Disable VTP synchronization:
The standard range consists of VLANs 1 to 1000.
The extended range consists of VLANs 1025 to 4096.