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Hands-On Lab: Configuring VTP Clients and Servers on Catalyst Switches

This hands-on lab configures VLAN Trunking Protocol between a server switch and a client switch, demonstrating how VLANs created on the server automatically propagate to the client without manual configuration on every device.

VTP Server ModeVTP Client ModeVLAN Propagation

~3 دقیقه مطالعه · آخرین به‌روزرسانی ۲۱ شهریور ۱۴۰۵

Lab Objective

Configure one switch as a VTP server and a second switch as a VTP client within the same VTP domain, then create a VLAN on the server and verify it automatically appears on the client.

Lab Purpose

Manually creating identical VLANs on every switch in a large network is tedious and error-prone. VTP allows VLAN database changes made on a server to propagate automatically to client switches, though this convenience comes with real risks that later labs will explore.

Lab Topology

SwitchServer ---- trunk link ---- SwitchClient

Both switches connected via a trunk port
already configured

Task 1: Configure the VTP Domain and Server Mode

On SwitchServer, configure the VTP domain name to CorpNet and explicitly set VTP mode to server.

Task 2: Configure the Client

On SwitchClient, configure the same VTP domain name and set VTP mode to client.

Task 3: Verify VTP Status on Both Switches

Confirm both switches show the same domain name and their respective correct VTP modes.

Task 4: Create a VLAN on the Server

Create VLAN 30 named Engineering on SwitchServer only.

Task 5: Verify Automatic Propagation to the Client

Confirm VLAN 30 automatically appears in SwitchClient's VLAN database without being manually configured there.

Solution and Verification

SwitchServer(config)# vtp domain CorpNet
SwitchServer(config)# vtp mode server

Setting device to VTP SERVER mode

SwitchClient(config)# vtp domain CorpNet
SwitchClient(config)# vtp mode client

Setting device to VTP CLIENT mode

SwitchServer# show vtp status

VTP Operating Mode           : Server
VTP Domain Name              : CorpNet
Configuration Revision       : 0

SwitchClient# show vtp status

VTP Operating Mode           : Client
VTP Domain Name              : CorpNet
Configuration Revision       : 0

SwitchServer(config)# vlan 30
SwitchServer(config-vlan)# name Engineering
SwitchServer(config-vlan)# exit

SwitchServer# show vtp status | include Revision

Configuration Revision       : 1
-- Notice the revision number incremented
-- from 0 to 1 the moment a VLAN was added --
-- this revision number is what SwitchClient
-- checks to know new information exists

SwitchClient# show vlan brief

VLAN Name       Status    Ports
---- ---------- --------- -----
30   Engineering active

-- VLAN 30 appeared automatically, even though
-- it was never manually typed on SwitchClient

Key Takeaway

VTP's revision number is the mechanism that triggers propagation — a client accepts VLAN database updates only when it receives a VTP advertisement with a HIGHER revision number than its own current database, which is exactly why understanding this number matters deeply when troubleshooting unexpected VLAN changes.

نوشته و پژوهش‌شده توسط دکتر شاهین صیامی

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