9.2 VTP  
  9.2.2 VTP concepts  
The role of VTP is to maintain VLAN configuration consistency across a common network administration domain. VTP is a messaging protocol that uses Layer 2 trunk frames to manage the addition, deletion, and renaming of VLANs on a single domain. Further, VTP allows for centralized changes that are communicated to all other switches in the network.

VTP messages are encapsulated in either Cisco proprietary Inter-Switch Link (ISL) or IEEE 802.1Q protocol frames, and passed across trunk links to other devices. In IEEE 802.1Q frames a 4 byte field is added that tags the frame. Both formats carry the VLAN ID.

While switch ports are normally assigned to only a single VLAN, trunk ports by default carry frames from all VLANs.

 

Web Links

VLAN Trunking Protocol Basics

http://infocenter.cramsession.com/
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