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S2700, S3700, S5700, S6700, S7700, and S9700 Series Switches Interoperation and Replacement Guide

This document provides typical configuration examples for interoperation between Huawei switches and mainstream IP phones, firewalls, routers, Microsoft NLB servers, multi-NIC servers, Cisco switches, and SolarWinds.
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Overview of VTP

Overview of VTP

The VLAN Trunking protocol (VTP), a Layer 2 protocol in the Open System Interconnection (OSI) model, manages VLAN creation, deletion, and renaming in a domain. VTP is a Cisco proprietary protocol.

Basic Concepts

VTP involves two important entities:
  • VTP domain

    A VTP domain is composed of switches that have the same VTP domain name and are connected through trunk links.

    Switches in a VTP domain share VLAN information, and each switch can join only one VTP domain. Switches in different VTP domains cannot share VLAN information.

  • Working mode

    VTP supports three working modes: VTP server, VTP client, and VTP transparent. For details, see Table 5-7.

    Table 5-7  Working mode of VTP

    Working Mode

    Description

    Server

    A VTP server maintains all VLAN lists in the local VTP domain. It can create, delete, and modify VLANs, send advertisement packets, and synchronize VLAN information to other switches in the local VTP domain.

    VLAN information is saved in the nonvolatile RAM (NVRAM).

    By default, a Cisco switch is used as the VTP server.

    Client

    A VTP client learns VTP information from a VTP server. It cannot create, delete, or modify VLANs, but can forward advertisement packets.

    VLAN information is not saved in NVRAM.

    Transparent

    A VTP transparent switch is an independent switch that does not participate in VTP implementation or learn VLAN information from the VTP server. It only maintains local VLAN information. The VTP transparent switch can create, delete, and modify only the local VLAN information.

    When VTP version 1 is used, VTP transparent switches can only forward VTP packets of other switches in the same VTP domain. When VTP version 2 is used, VTP transparent switches can forward VTP packets of switches in a different VTP domain.

Advertisement Packets

Switches use VTP advertisement packets to transmit VLAN information. Table 5-8 describes three types of VTP advertisement packets.
Table 5-8  Format of advertisement packets

Format

Applicable Scenario

Summary Advertisement

  • By default, a VTP server sends a Summary Advertisement packet every 300s to inform adjacent switches of the current VTP domain name and the configuration revision number.

    When a switch receives a summary advertisement packet, the following situations occur:
    1. The switch compares the VTP domain name with its own VTP domain name. If the names are different, the switch ignores the packet.
    2. If the names are the same, the switch compares the configuration revision number with its configuration revision number.
    3. If its configuration revision number is higher than or equal to the configuration revision number in the Summary Advertisement packet, the switch ignores the packet. If its configuration revision number is lower than the configuration revision number in the Summary Advertisement packet, the switch sends an Advertisement Request packet.
  • When a switch receives an Advertisement Request packet, it sends a Summary Advertisement packet, and then sends one or several Subset Advertisement packets.

Subset Advertisement

When you add, delete, or change a VLAN on a switch, the VTP server where the changes are made increments the configuration revision number and sends a Summary Advertisement packet. Then the VTP server sends one or more Subset Advertisement packets. A subset advertisement contains a list of VLAN information. If there are several VLANs, the VTP server needs to send more than one Subset Advertisement packet to advertise all the VLANs.

Advertisement Request

A switch needs an Advertisement Request packet in the following situations:
  • The switch restarts.
  • The VTP domain name has been changed.
  • The switch has received a Summary Advertisement packet with a higher configuration revision number than its own.
VTP advertisement packets have the following characteristics:
  • VTP advertisement packets are transmitted in multicast mode through trunk interfaces in VLAN 1.
  • VTP advertisement packets are sent to the destination MAC address 01-00-0C-CC-CC-CC.
  • VTP advertisement packets are sent in either Inter-Switch Link (ISL) or IEEE 802.1Q (dot1q) frames.
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Updated: 2019-05-15

Document ID: EDOC1000114005

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