VTP Configuration
VTP sends updates out all active trunk interfaces (ISL or 802.1Q). However, with all default
settings from Cisco, switches are in server mode, with no VTP domain name configured, and they
do not send any VTP updates. Before any switches can learn VLAN information from another
switch, at least one switch must have a bare-minimum VTP server configuration—specifically,
a domain name.
Example 2-4 shows Switch3 configuring a VTP domain name to become a VTP server and
advertise the VLANs it has configured. The example also lists several key VTP show commands.
(Note that the example begins with VLANs 21 and 22 configured on Switch3, and all default
settings for VTP on all four switches.)
Example 2-4 VTP Configuration and show Command Example
! First, Switch3 is configured with a VTP domain ID of CCIE-domain.
Switch3# conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch3(config)# vtp domain CCIE-domain
Changing VTP domain name from NULL to CCIE-domain
Switch3(config)# ^Z
! Next, on Switch1, the VTP status shows the same revision as Switch3, and it
! learned the VTP domain name CCIE-domain. Note that Switch1 has no VTP-related
VLAN Trunking Protocol 41
Example 2-4 shows examples of a few VTP configuration options. Table 2-4 provides a complete
list, along with explanations.
! configuration, so it is a VTP server; it learned the VTP domain name from.
! Switch3.
Switch1# sh vtp status
VTP Version : 2
Configuration Revision : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs : 7
VTP Operating Mode : Server
VTP Domain Name : CCIE-domain
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x0E 0x07 0x9D 0x9A 0x27 0x10 0x6C 0x0B
Configuration last modified by 10.1.1.3 at 3-1-93 00:02:55
Local updater ID is 10.1.1.1 on interface Vl1 (lowest numbered VLAN interface found)
! The show vlan brief command lists the VLANs learned from Switch3.
Switch1# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/6, Fa0/7, Fa0/10
Fa0/11, Fa0/13, Fa0/14, Fa0/15
Fa0/16, Fa0/17, Fa0/18, Fa0/19
Fa0/20, Fa0/21, Fa0/22, Fa0/23
Gi0/2
21 VLAN0021 active
22 ccie-vlan-22 active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
Table 2-4 VTP Configuration Options
Option Meaning
domain Sends domain name in VTP updates. Received VTP update is ignored if it does not
match a switch’s domain name. One VTP domain name per switch is allowed.
password Used to generate an MD5 hash that is included in VTP updates. Received VTP
updates are ignored if the passwords on the sending and receiving switch do not
match.
mode Sets server, client, or transparent mode on the switch.
continues
Example 2-4 VTP Configuration and show Command Example (Continued)
Option Meaning
version Sets version 1 or 2. Servers and clients must match version to exchange VLAN
configuration data. Transparent mode switches at version 2 forward version 1 or
version 2 VTP updates.
pruning Enables VTP pruning, which prevents flooding on a per-VLAN basis to switches that
do not have any ports configured as members of that VLAN.
interface Specifies from which interface a switch picks the source MAC address for VTP
updates.