What is Dynamic Trunking Protocol (DTP)?
In addition to the issue of how to transport VLAN’s between switches, there are a couple of other potential issues that arise when you start trunking. The first issue is that both ends of a trunk cable had better agree they’re trunking, or they’re going to be interpreting trunk frames as normal frames. End stations will be extremely puzzled by the extra tag information in the frame header, their driver stacks won’t understand it, and the end systems may lock up or fail in odd ways. Not fun to troubleshoot! To resolve this, Cisco came up with a protocol for switches to communicate intentions. The first version of it was VTP, VLAN Trunking Protocol, which worked with ISL. The newer version works with 802.1q as well, and is called Dynamic Trunking Protocol (DTP), so you can tell it apart from VTP. The second issue is creating VLAN’s. If you have to configure VLAN’s individually, switch by switch, you have a lot of work to do. Worse, there’s a danger of inconsistency, whereby VLAN 100 is E
