VLAN Trunk Protocol (VTP) is a Cisco-proprietary protocol used to replicate VLANs using Layer 2 frames to other switches. It is a method to ease administration by selecting a switch to be configured as a VTP server.
VLANs are arranged on the VTP server and after that imitated to other associated switches, called VTP clients. This decreases the sum of setup — having to log onto each switch to form a VLAN. All VLAN and VTP data is spared within the vlan.dat record – put away within the switch’s streak memory.
VTP Domain
VTP is organized into administration, which share common VLAN prerequisites. These administration spaces are called VTP Spaces. A switch can as it were be joined to one VTP space. Each VTP space is separated from one another. Data isn’t shared between VTP spaces.
VTP Modes
Server Mode – switch has full control over creating and modifying VLANs.
Client Mode – switch cannot create, modify, or delete any VLANs.
Transparent Mode – switch doesn’t participate in VTP. A switch in Transparent Mode will forward VTP version 2 VTP Advertisements.
VTP Advertisements
VLAN Trunk Protocol are multicast outlines carrying VTP data. To prepare a VTP Promotion, a switch must have the same VTP secret word and space designed. Diverse promotions are followed with arrangement amendment numbers. When changes are made by a VTP server, the modification number is increased some time recently sending the notice out. There can be three diverse advertisements
Summary advertisements – sent out every 300 seconds and every time a change occurs on the VLAN database. Contained in a summary advertisement:
- VTP version
- Domain name
- Configuration revision number
- Time stamp
- MD5 encryption hash code
Subset advertisements – sent after a VLAN configuration change occurs. Contained in the subset advertisement is a list including:
- VLAN / VLAN type
- MTU
- Length of the VLAN name/ VLAN number
- Security association identifier value
Advertisement requests from clients – which is a VTP client requesting any VLAN information it needs.
Configuring VTP
By default, a switch will have a domain name of NULL and no password. If the switch hears a VTP advertisement it will automatically learn the VTP domain name, VLANs, and the configuration revision number.
In global configuration mode, configure the VTP domain name
SW1#conf t Enter configuration commands, one per line. End with CNTL/Z. SW1(config)#vtp domain mobileinfoworld.com
Then configure the VTP mode and password:
SW1(config)#vtp mode ? client Set the device to client mode. server Set the device to server mode. transparent Set the device to transparent mode. SW1(config)#vtp mode server SW1(config)#vtp password Sup0r!S3cret@ Setting device VLAN database password to Sup0r!S3cret@
Configure VTP version 2
SW1(config)# vtp version 2
VTP pruning increases the efficiency of trunk bandwidth by reducing the amount of flooded traffic. Basically, broadcast and unknown unicast frames are not forwarded over a trunk link if the receiving switch doesn’t have any ports on that particular VLAN.
Enable VTP pruning
SW1(config)# vtp pruning
Verify VTP
View VTP parameters with show vtp status
SW1#show vtp status VTP Version : running VTP2 Configuration Revision : 1 Maximum VLANs supported locally : 1005 Number of existing VLANs : 6 VTP Operating Mode : Server VTP Domain Name : mobileinfoworld.com VTP Pruning Mode : Disabled VTP V2 Mode : Enabled VTP Traps Generation : Disabled MD5 digest : 0x8D 0x95 0xC5 0x2C 0xC8 0x83 0xB9 0x3C Configuration last modified by 10.1.1.100 at 3-1-93 11:24:38 Local updater ID is 10.1.1.100 on interface Vl10 (lowest numbered VLAN interface found) SW1#
Final
SW1> en SW1# conf t SW1(config)#vtp domain mobileinfoworld.com SW1(config)#vtp mode server SW1(config)#vtp password Sup0r!S3cret@ SW1(config)#vtp version 2
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