3 Modes of VLAN Trunking Protocol(VTP), You should Know About it.

VLAN Trunking Protocol – VTP


VLAN Trunking Protocol is a protocol used between switches to simplify the management of VLANs. Cisco proprietary VTP is used to create, manage and maintain a large network with many interconnected switches. With VTP, you can make configuration changes centrally on a single catalyst series switch and have those changes automatically communicated to all the others switches in the network. VTP can manage the addition, deletion and renaming of VLANs from a central point without any manual intervention. This reduces network administration in a switch network. VTP can be sent any changes advertisement over 802.1Q and ISL trunks. It has three modes, namely, server, client and Transparent.

How does VTP work?

Example

Assume there are 15 switches with 30 VLANs. VLAN information such as numbers, names must be configured in every switch and the same process of configuring all switches must be repeated if new VLANs are added. This becomes an administrative overhead and a time-consuming task. To address this issue, Cisco developed a solution called the VLAN Trunking Protocol (VTP). In a VLAN Trunking Protocol, all Information from the VTP server switch will be synchronized to the VTP client switches. By default, all the Cisco switches will be in the server mode even when there are multiple VTP servers.
In the configuration of VTP, one of the switches should be configured as VTP server. All switches present in the VTP must have in the single domain. VLAN Trunking Protocol should have the same version in all VTP servers and VTP clients’ switches.

VTP working Process

  • The user should Identify the switches that should act as the VTP server (normally, this would be the core switch). Also, identify client switches.
  • Next, configure the VTP domain in the server and assign the same domain name to all other client switches. (by default no VTP domain is assigned to switches)
  • Create a VTP password for preventing unauthorized access of any VTP client to the network (this is optional).
  • With this, the VTP server and clients start to synchronize. Whenever there are changes or additions in the VTP server, the switches will be advertised to all  the client switches

VTP Modes

The different types of VTP modes are as shown

VTP, vtp modes, 3 modes, server modes, client modes, transparent mode
VLAN Trunking Protocol

Also Read:

Three Steps to Configure VLAN Properly.


The features of the 3 modes of VTP are given below

Server Mode:

  • VLAN Trunking Protocol server is the default mode of all switches
  • It sends VLAN configuration to other switches in the same VTP domain.
  • It will synchronize other switches based on advertisements received on trunk links
  • If there any changes made in the domain while the server mode will be advertised to the entire VTP domain.

VTP, server mode, client Mode, transparent mode
VLAN Trunking Protocol

Configuration

SW1 (config)#  vtp mode server
Device mode already vtp sever
Sw1 (config)# vtp domain inforamtionalduniya.com
Changing VTP domain name from null to informationalduniya.com
Sw1 (config)# vtp password 123456
Setting device VLAN database password to 123456

 

Client Mode

  • In this mode switch received information from the VTP servers
  • It sends and receives updates
  • VLAN information is received from the VLAN Trunking Protocol server.

Configuration

Sw2 (config)# vtp mode client
Setting the device to vtp client mode.

Transparent VTP mode

  • Transparent mode Switches do not participate in the VTP domain.
  • These Switches can add and create VLANs.
  • Switches do not advertise, hence do not accept VLAN based on the advertisement, but forwards VTP advertisements receive by trunk ports.
  • The function of the transparent mode is to forward the VTP summary advertisements but do not take part in the VLAN tasks.

Configuration

Sw2 (config)# vtp mode client
Setting the device to vtp client mode

VTP advertisements

Each switch in the VLAN Trunking Protocol domain sends regular advertisements from each trunk port to a reserved multicast address. VTP advertisements are received by neighbouring switches, which update their VTP and VLAN configurations as and when necessary.
  • The below global configuration information is distributed in VTP advertisements:
  • VLAN IDs (ISL and 802.1Q)
  • Emulated LAN names (for ATM LANE)
  • 802.10 SAID values (FDDI)
  • VTP domain name
  • VTP configuration revision number
  • VLAN configuration, including maximum transmission unit (MTU) size for every VLAN
  • Frame format.

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