The Dynamic Trunking Protocol (DTP) is a
proprietary networking protocol
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.
Intellectual property rights and enforcement
Ownership by a single organization gives the owner the ability to place restricti ...
developed by
Cisco Systems
Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational corporation, multinational digital communications technology conglomerate (company), conglomerate corporation headquartered in San Jose, California. Cisco develo ...
for the purpose of negotiating
trunking
In telecommunications, trunking is a technology for providing network access to multiple clients simultaneously by sharing a set of circuits, carriers, channels, or frequencies, instead of providing individual circuits or channels for each clie ...
on a link between two
VLAN
A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer (OSI layer 2).IEEE 802.1Q-2011, ''1.4 VLAN aims and benefits'' In this context, virtual, refers to a physi ...
-aware
switches
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
, and for negotiating the type of trunking
encapsulation to be used. It works on
Layer 2
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer pr ...
of the
OSI model
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
. VLAN trunks formed using DTP may utilize either
IEEE 802.1Q
IEEE 802.1Q, often referred to as Dot1q, is the networking standard that supports virtual local area networking (VLANs) on an IEEE 802.3 Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying proce ...
or
Cisco ISL trunking protocols.
DTP should not be confused with
VTP, as they serve different purposes. VTP communicates VLAN existence information between switches. DTP aids with trunk port establishment. Neither protocol transmits the data
frames that trunks carry.
Switch port modes
The following switch port mode settings exist:
* ''Access'' — Puts the
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
port into permanent nontrunking mode and negotiates to convert the link into a nontrunk link. The Ethernet port becomes a nontrunk port even if the neighboring port does not agree to the change.
* ''Trunk'' — Puts the Ethernet port into permanent trunking mode and negotiates to convert the link into a trunk link. The port becomes a trunk port even if the neighboring port does not agree to the change.
* ''Dynamic Auto'' — Makes the Ethernet port willing to convert the link to a trunk link. The port becomes a trunk port if the neighboring port is set to trunk or ''dynamic desirable'' mode. This is the default mode for some switchports.
* ''Dynamic Desirable'' — Makes the port actively attempt to convert the link to a trunk link. The port becomes a trunk port if the neighboring Ethernet port is set to trunk, ''dynamic desirable'' or ''dynamic auto'' mode.
* ''No-negotiate'' — Disables DTP. The port will not send out DTP frames or be affected by any incoming DTP frames. If you want to set a trunk between two switches when DTP is disabled, you must manually configure trunking using the (switchport mode trunk) command on both sides.
The configured switch port mode setting is referred to as the port's ''trunking administrative mode''. The current behavior of a given port after negotiating with the neighboring port is referred to as the port's ''trunking operational mode''.
See also
*
GARP VLAN Registration Protocol
Multiple Registration Protocol (MRP), which replaced Generic Attribute Registration Protocol (GARP), is a generic registration framework defined by the IEEE 802.1ak amendment to the IEEE 802.1Q standard. MRP allows bridges, switches or other simil ...
*
Multiple VLAN Registration Protocol
Multiple Registration Protocol (MRP), which replaced Generic Attribute Registration Protocol (GARP), is a generic registration framework defined by the IEEE 802.1ak amendment to the IEEE 802.1Q standard. MRP allows bridges, switches or other simil ...
References
{{Reflist
External links
Disabling Dynamic Trunking Protocol (DTP) Stretch, Jeremy. Retrieved 1 June 2016.
Cisco protocols
Ethernet