VTP (VLAN Trunking Protocol): VLAN trunking protocol, which is a Cisco-specific protocol. Also known as the Virtual Local Area Network Protocol. It is a Cisco proprietary agreement. In a network with many switches, the workload of configuring VLANs is heavy. You can use the VTP protocol to configure one switch as a VTP Server and the other switches as VTP Clients, so that they can synchronize VLAN information.
The VLAN Relay Protocol (VTP) uses Layer 2 relay frames to perform VLAN communication between a group of switches. VTP starts from a central control point and maintains the addition, addition, and renaming of VLANs throughout the enterprise network, ensuring the consistency of configuration. Generally speaking, we need to maintain the synchronization of the VLAN database among the switches in the entire network to ensure that all switches can read the relevant VLAN information for correct data forwarding. However, for large networks, the number of switches as access devices must be many, and there may be dozens of VLANs on a switch. If manually configured, it is a very large workload and is not conducive to maintenance. In this case, we introduced VTP (VLAN Trunking Protocol).
There are 3 kinds of server mode, client mode and transparent mode in VTP mode. The default configuration of the new switch at the factory is pre-configured to VLAN1, and the VTP mode is server. There is only one VTP Server for the entire network in a VTP domain. The VTP Server maintains a list of all VLAN information in the VTP domain. The VTP Server can create, delete, or modify VLANs, send and forward related announcement information, and synchronize vlan configurations. Although the VTP Client also maintains a list of all VLAN information, its VLAN configuration information is learned from the VTP Server. The VTP Client cannot create, delete, or modify VLANs, but can forward advertisements and synchronize vlan configurations. VTP Transparent is equivalent to an independent switch, it does not participate in VTP work, does not learn VLAN configuration information from the VTP Server, but only has the VLAN information maintained by the device itself. VTP Transparent can create, delete and modify the VLAN information on this machine, meanwhile it will forward the announcement and save the configuration.
To use VTP, you must first establish a VTP domain so that it can manage the current VLAN on the network. Switches in the same management domain share their VLAN information, and a switch can only participate in one management domain. Switches in different domains cannot share VLAN information.
VTP maintains uniformity of VLAN configuration through the network (ISL frames or cisco private DTP frames). VTP adds, deletes, and adjusts VLANs at the system level to automatically broadcast information to other switches in the network. In addition, VTP reduces the configuration that may cause security problems. Easy to manage, as long as the corresponding settings are made on the vtp server, the vtp client will automatically learn the vlan information on the vtp server.
The VTP domain is also called the VLAN management domain, and it is composed of more than one switches that share the VTP domain name and are connected to each other. In other words, a VTP domain is a group of switches with the same VTP domain name and connected to each other through a trunk link. VTP domain requirements:
1. Every switch in the domain must use the same domain name, whether it is achieved through configuration or automatically learned by the exchange.
2. Catalyst switches must be adjacent, that is, adjacent switches need to have the same domain name.
3. A trunk link must be configured between all Catalyst switches.
If any of the above conditions are not met, the VTP domain cannot be connected, and the information cannot be transmitted across the separated parts.
VTP message type:
1. Summary notice
By default, the Catalyst switch sends a summary announcement message every 5 minutes. The summary announcement informs the neighboring Catalyst switch of the current VTP domain name and configuration revision number. When the switch receives the summary announcement message data packet, the switch compares the VTP domain name in the data packet with its own VTP domain name. If the name is different, the switch will ignore the packet. If the names are the same, the switch compares its configuration revision number with the data packet revision number. If the revision number of your configuration is greater than or equal to the revision number of the data package, the data package will also be ignored. If your configuration revision number is relatively small, the switch will send an announcement request message.
2. Subset notice
When an administrator adds, deletes, or modifies a VLAN on a Catalyst switch, the server switch whose configuration has been modified will increase the configuration revision number and send a summary notification message. Subsequently, it will send one or more subset announcement messages. Each subset announcement message contains a list of VLAN information. If there are multiple VLANs, the switch will request the server switch to send multiple subset advertisement messages to announce all the information of these VLANs.
3. Notification request
In the following cases, the switch needs to send a VTP announcement request message.
1. Switch reboot
2. VTP domain name is modified
3. The switch receives a VTP summary announcement message, and the configuration revision number of the message is higher than its own revision number.
After receiving the notification request message, the VTP device will send a summary notification message. After this, one or more subset announcement messages are sent.
Configure the VTP domain name: switch(config)#vtp domain test
Configure VTP operating mode: switch(config)#vtp mode server
Configure password: switch(config)#vtp password mypassword
View configuration: switch(config)#show vtp status
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