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VLAN Trunking Protocol (VLAN Trunking Protocol)
Cisco Private Protocol, which manages the creation, deletion, and renaming of VLANs within the network range of the same domain.
When you configure a new VLAN on a server switch, the configuration information for the VLAN is propagated to all other switches in the domain through VTP advertisement packets. These switches automatically receive this configuration information, aligning their VLAN configuration with the Server switch, reducing the effort of configuring the same VLAN information on multiple devices and maintaining the uniformity of VLAN configuration.
- Condition 1: Interconnects between switches use a Trunk link.
- Condition 2: The same non-empty VTP domain name and key are the same between the switches.
- VTP mode: Server mode (core), Client mode, and transparent mode
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VTP message type:
(Using 802.3 package, multicast address 01-00-0C-CC-CC-CC sent);
1. Summary Advertisements
By default, the Server switch sends a summary advertisement message every 5 minutes to notify the neighbor switch of the current VTP domain name and configuration revision number.
When a neighbor switch receives a packet of rollup advertisement messages, it compares the VTP domain name in the packet with its own. If the domain names are different, the switch ignores the packet. If the domain names are the same, the switch compares its own configuration revision number to the revision number of the packet.
If your own configuration revision number is smaller than the revision number of the packet, you will learn the VLAN information. If its own configuration revision number is larger, the switch ignores the packet and sends an advertisement request message to the Server switch; if the configuration revision number value is the same, it ignores and does not send any advertisement.
2. Subset Advertisements
When an administrator adds, removes, or modifies a VLAN on a Server switch, the configuration revision number value of the switch is +1 and a summary advertisement message is sent, followed by one or more subset notification messages, each of which contains the details of a VLAN.
3. Request Advertisements
The switch needs to send a VTP advertisement request message to the Server switch in the following cases.
--The switch is connected to the network for the first time or rebooted
--The VTP domain name was modified
--When a new switch is added to the domain, the server switch receives a VTP summary advertisement message with a configuration revision number higher than its own.
After receiving the advertisement request message, the Server switch sends a summary advertisement message. After that, send one or more subset notification messages.
1. VTP version: VTP1, VTP2, VTP3; when the VTP domain name of the switch is empty, the VTP domain name and version number can also be automatically synchronized;
2, Server mode switch, in VTP1, VTP2 version, can only create standard VLAN, in the VTP3 version, you can create all VLANs; it is recommended that all server switches in the domain enable VTP trimming function, reduce the flood range of broadcast / multicast; when the value of the configuration revision number of the two server switches is the same, the VLAN can not be synchronized, at this time you can check the value of the VTP checksum MD5 on the switch, Then modify the value of the configuration revision number of one of the switches (add/remove VLANs);
3. If you modify the domain name of the switch or change it to transparent mode, you can zero out the value of the switch configuration revision number.
VTP pruning: VTP Pruning, a feature of VTP, which can reduce unnecessary traffic flooding on trunk ports; reduce broadcasting, multicast, unicast, reserved bandwidth, VTP pruning only send broadcasts on trunk links. By default, VTP pruning on Cisco switches is turned off by default; when you enable VTP pruning on the VTP server, VTP pruning is enabled for the entire VTP domain, and VLAN synchronization occurs between the switches
Each switch will know which VLAN access members exist on the neighbor switch, and when it receives broadcast or multicast traffic sent by vlan10 members, it will not flood to the switch without vlan10 members.
Note: The default VTP pruning can only be in VLAN 2 through VLAN 1005, VLAN 1 is the management VLAN;
Note: In order to ensure the security of the VTP domain, the VTP domain can set a password, and all switches in the domain must set the same password; VTP can only work normally after the same password is configured for the switches in the VTP domain. The switch that does not know the password or the password is wrong speaks of the message that cannot get the VLAN. However, some unfortunately, the VTP domain password is passed in clear text over the network.
The above is today's knowledge sharing, more questions You can leave a message in the comment area to discuss! Thank you very much for your support!