DTP (Dynamic Trunking Protocol)
❖ DTP is a Cisco Layer 2 Protocol used to dynamically negotiate a
Switchport into a Trunk without manual configurations.
❖ It can negotiate a status of a Port into a Trunk or an Access Port but the
aim of it being in forming a Trunk rather than an Access Port since all
Switchports are Access ports by default.
❖ DTP is enabled by default on all Cisco Switch Interfaces.
❖ For Security Purposes, Trunk manual configurations is recommended and
not the use of DTP. DTP should be disabled on all Switchports using
command: switch(config-if)#switchport nonegotiate
DTP (Dynamic) Switchport Modes
❖ There are Two (2) dynamic Switchport Modes for DTP these are;
a) Dynamic Desirable Mode
➢ A Switchport in dynamic desirable mode will actively
trying to form a Trunk with other Cisco Switches.
➢ It will form a Trunk with other Switch in the following modes;
switchport mode trunk (Manual Trunk Config)
switchport mode dynamic desirable
switchport mode auto
b) Dynamic Auto Mode
➢ A Switchport in dynamic auto mode will NOT actively
trying to form a Trunk with other Cisco Switches.
➢ It will form a Trunk with other Switch in the following modes;
switchport mode trunk (Manual Trunk Config)
switchport mode dynamic desirable
HOW TO COFIGURE DTP IN VARIOUS MODES
1. Enter an interface mode to an interface that you want to configure a DTP
Switch(config)#interface GigabitEthernet 0/1
Switch(config-if)#
2. Configure Dynamic Trunking Protocol per interface in any of the below
cases;
CASE A: Dynamic Desirable Vs Dynamic Desirable
CASE B: Dynamic Desirable Vs Trunk or Vice Versa
CASE C: Dynamic Desirable Vs Dynamic Auto or Vice Versa
CASE D: Dynamic Auto Vs Trunk or Vice Versa
CASE E: Dynamic Auto Vs Dynamic Auto
N.B;
➢ For Case E and all other configurations combinations (which wasn’t
listed above) will not form a Trunk.
3. Verify your configurations
➢ Use below commands to verify your Trunk Configurations;
Switch#show interfaces trunk
Or
Switch#show interfaces GigabitEthernet 0/1
switchport
N.B;
➢ The Last Command (show interfaces GigabitEthernet 0/1
Switchport) is a more detailed one.
➢ View the Trunk information under Administrative Mode and
Operational Mode.
VTP (VLAN TRUNKING PROTOCOL)
❖ VTP is a Cisco Proprietary Protocol used to dynamically add, remove and
change normal range VLANs across all switches in a Network.
❖ It is designed for larger networks with many VLANs, so you don’t have to
configure each VLAN on every Switch.
❖ It is rarely used and it is recommended that you don not use it for security
reasons.
❖ There are Three (3) Versions of VTP: 1, 2 and 3.
VTP OPERATING MODES
➢ There are Three (3) VTP Operating Modes for Cisco Switches;
1. VTP Server
▪ A Switch acting as a VTP Server can add, delete or change VLANs
on other VTP Servers or Clients.
▪ By Default, all Cisco Switches operates as VTP Servers.
2. VTP Client
▪ A Switch configured as a VTP Client can not add, delete or change
VLANs on other VTP Servers or Clients.
3. VTP Transparent
▪ Merely forwards VTP Advertisement messages but doesn’t
participate in the adding, deleting or changing of VLANs.
▪ It doesn’t update its own VLAN Database, it has its own VLAN.
VTP KEY SETTINGS AND FEATURES:
1. VTP Domain
➢ Is the name shared among all switches in the same group or domain
2. VTP Password
➢ Password configured and shared to all Switches in the same VTP Domain.
➢ Used for authentication purposes.
3. VTP Version
➢ Either Version 1, 2 or 3.
➢ Version 3 supports Extended VLAN range (1006 – 4094) and it is
supported on the new Cisco Switches.
4. VTP Revision Number
➢ The VTP Server with the highest revision number will overwrite the
VLANs in the Switches with lower revision numbers.
HOW TO CONFIGURE VTP
1. Verify Trunking between Switches if no Trunking configure Trunk links
between the Switches either manually or using DTP.
2. Configure VTP Domain name to be used by all Switches in a Network
Switch(config)#vtp domain Domain-name
3. Set Password (optional) to be used for authentication
Switch(config)#vtp password password
4. Create /Modify/Delete VLANs in one of the VTP Server and observe to
other Switches.
5. Verify your VTP configurations
Switch#show vtp status
