VLAN TRUNKING PROTOCOL
Configuring VLAN and VLAN trunking for large networks with many
interconnected switches can be a very difficult task. VTP is a protocol created by Cisco
to create
and manage VLANs for a large network with many interconnected switches
.
VTP is a very useful protocol to
create, manage and maintain a large network with many interconnected switches.
The VTP can manage the addition,
deletion, and renaming of VLANs from a central
point without
manual intervention and VTP thus reduces network administration in a switched network.maintain
consistency throughout the network. In other words, switches use VTP to communicate among
themselves about VLAN configuration.
VTP is organized into
management domains. A VTP domain is one switch or
several interconnected switches sharing the same VTP environment. A switch
can be configured only in one VTP domain. Switches in different VTP domains do not share VTP information.
With the a VTP
Password, you can prevent unwanted VTP server switches in the network. By using
a VTP password switches can only be a client of a VTP Server if the passwords
match.
Switches in a VTP domain advertise many VLAN attributes to their VTP domain neighbors. These
VLAN advertisements contain information about the VTP management domain, VTP
revision number, available VLANs, and other VLAN parameters. VTP revision number is important because it determines which updates
are to be used when not managed properly this number can cause the deletion of
all your networks VLAN information.
When you set a VTP Domain Name,
the revision number is set to zero, after which each change to the VLAN
database increases the revision number by one. When a switch receives VTP
information from a neighboring switch, the first switch processes data only for
the same domain when the revision number is higher than its own.
A network switch participating in VTP, can have
three different modes.
• Server Mode
VTP Server
Mode
VTP server mode is the default VTP mode for all Catalyst switches. At
least one server is required in a VTP domain topropagate VLAN information
within the domain. We can create, add, or delete VLANs on a VTP domain VTP
Server and change VLAN information in a VTP Server. The changes made in a
switch in server mode are advertised to the entire VTP domain.
VTP Client
Mode
VTP client mode switches listen to VTP advertisements from other switches
and modify their VLAN configurations accordingly. A network switch in
VTP client mode requires a server switch to inform it about the VLAN
changes. We Can not create, add, or delete VLANs in a VTP client.
VTP Transparent Mode
VTP transparent mode switches do not participate in the VTP domain, but VTP
transparent mode switches can receive and forward VTP advertisements through
the configured trunk links.
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