VTP is Vlan Trunking Protocol. Cisco proprietary.
Purpose: To enable the automatic configuration of VLANS in a switch. Once one switch is configured as a server, the client will create all VLANS on the server.
VTP Modes: Server, client, transparent.
Server: Set up VTP server and VLANS will propagate to clients. Server sends out VTP advertisements.
Client: Receives advertisements and updates VLAN database
Transparent: Forwards VTP advertisements but does not update database.
VTP pruning: VTP broadcasts only if switch on receiving end has ports in that VLAN.
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DTP is Dynamic Trunking Protocol. Cisco Proprietary
Purpose: To dynamically form trunks with other Cisco Switches
The DTP is used by Cisco switches to negotiate whether an interconnection between two switches should be put into access or trunk mode. It is meant both to ease the initial deployment of a switched network and to minimize configuration errors that result from mismatched port configuration on an interconnection between two switches.
The DTP helps to automatically negotiate whether the port should be put into access or trunk mode and what trunking protocol (802.1Q or ISL) should be used. The individual DTP modes are:
- dynamic auto – the port will negotiate the mode automatically, however, it prefers to be an access port
- dynamic desirable – the port will negotiate the mode automatically, however, it prefers to be a trunk port
DTP datagrams are also sent if the port is set statically to the trunk mode. However, if the port is set statically to the access mode, both sending and processing DTP datagrams on that port is deactivated.
The individual combinations of port settings lead to following results:
- dynamic auto + dynamic auto = access
- dynamic auto + dynamic desirable = trunk
- dynamic desirable + dynamic desirable = trunk
- dynamic auto or dynamic desirable + trunk = trunk
- dynamic auto or dynamic desirable + access = access
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