31 Days Before Your CCNA Exam

Day 22 99Example 22-2Configuring the VTP ServerS1#config tEnter configuration commands, one per line. End with CNTL/Z.S1(config)#vtp mode serverDevice mode already VTP SERVER.S1(config)#vtp password ciscoSetting device VLAN database password to ciscoS1(config)#vtp domain CCNAChanging VTP domain name from NULL to CCNAS1(config)#end%SYS-5-CONFIG_I: Configured from console by consoleS1#Note We configured the VTP password before the VTP domain name for a specific reason.As soon as the VTP domain name is configured, S1 will begin sending out VTP messageson all trunk links that are active. If switches on the other end of the trunk are using thedefault VTP configuration (server mode, null as the domain name, and no password), theywill start using the domain name sent in the VTP messages. This can cause VLAN databasecorruption if the receiving switch has a higher configuration revision number than the configuredserver. The receiving switch is also a VTP server and will send out its VLAN databaseto the configured VTP server. By configuring the password first, we avoid the potential forthis to happen. After the switches on the other end of the trunks are configured as clients,their configuration revision number is reset to 0. Then when the domain name and passwordare configured, VTP updates will be requested from the VTP server.We explicitly configured S1 as a VTP server instead of assuming it is in the default VTP servermode. Example 22-3 shows the commands used to verify the configuration.Example 22-3Verifying the VTP ConfigurationS1#show vtp statusVTP Version : 2Configuration Revision : 0Maximum VLANs supported locally : 64Number of existing VLANs : 5VTP Operating Mode: ServerVTP Domain Name: CCNAVTP Pruning Mode: DisabledVTP V2 Mode: DisabledVTP Traps Generation: DisabledMD5 digest: 0x8C 0x29 0x40 0xDD 0x7F 0x7A 0x63 0x17Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00Local updater ID is 0.0.0.0 (no valid interface found)S1#show vtp passwordVTP Password: ciscoS1#