Vtp; Vtp Overview - Cisco Nexus 7000 Series Configuration Manual

VTP

VTP
VTP is a Layer 2 messaging protocol that maintains VLAN consistency by managing the addition, deletion,
and renaming of VLANs within a VTP domain. A VTP domain is made up of one or more network devices
that share the same VTP domain name and that are connected with trunk interfaces. Each network device can
be in only one VTP domain.
Layer 2 trunk interfaces, Layer 2 port channels, and virtual port channels (vPCs) support VTP functionality.
The VTP is disabled by default on the device. You can enable and configure VTP using the command-line
interface (CLI). When VTP is disabled, the device does not relay any VTP protocol packets.
Note Before Release 5.1(1), VTP worked only in transparent mode in the Cisco Nexus 7000 Series devices,
allowing you to extend a VTP domain across the device.
When the device is in the VTP transparent mode, the device relays all VTP protocol packets that it receives
on a trunk port to all other trunk ports. When you create or modify a VLAN that is in VTP transparent mode,
those VLAN changes affect only the local device. A VTP transparent network device does not advertise its
VLAN configuration and does not synchronize its VLAN configuration based on received advertisements.
VLAN 1 is required on all trunk ports used for switch interconnects if VTP is supported in the network.
Note
Before 7.2(0)D1(1), disabling VLAN 1 from any of these ports prevents VTP from functioning properly.
If you enable VTP, you must configure either version 1 or version 2. If you are using VTP in a Token Ring
environment, you must use version 2.

VTP Overview

VTP allows each router or LAN device to transmit advertisements in frames on its trunk ports. These frames
are sent to a multicast address where they can be received by all neighboring devices. They are not forwarded
by normal bridging procedures. An advertisement lists the sending device's VTP management domain, its
configuration revision number, the VLANs which it knows about, and certain parameters for each known
VLAN. By hearing these advertisements, all devices in the same management domain learn about any new
VLANs that are configured in the transmitting device. This process allows you to create and configure a new
VLAN only on one device in the management domain, and then that information is automatically learned by
all the other devices in the same management domain.
Once a device learns about a VLAN, the device receives all frames on that VLAN from any trunk port by
default, and if appropriate, forwards them to each of its other trunk ports, if any. This process prevents
unnecessary VLAN traffic from being sent to a device. An extension of VTP called VTP pruning has been
defined to limit the scope of broadcast traffic and save bandwidth. Beginning with Release 5.1(1), the Cisco
NX-OS software supports VTP pruning.
VTP also publishes information about the domain and the mode in a shared local database that can be read
by other processes such as Cisco Discovery Protocol (CDP).
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x
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Configuring VTP