Understanding The Vtp Domain; Understanding Vtp Modes; Understanding Vtp Advertisements - Cisco 6500 Series Software Configuration Manual

Understanding How VTP Works

Understanding the VTP Domain

A VTP domain (also called a VLAN management domain) is made up of one or more interconnected
network devices that share the same VTP domain name. A network device can be configured to be in one
and only one VTP domain. You make global VLAN configuration changes for the domain using either
the command-line interface (CLI) or Simple Network Management Protocol (SNMP).
By default, the Catalyst 6500 series switch is in VTP server mode and is in the no-management domain
state until the switch receives an advertisement for a domain over a trunk link or you configure a
management domain.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name
and the VTP configuration revision number. The switch ignores advertisements with a different
management domain name or an earlier configuration revision number.
If you configure the switch as VTP transparent, you can create and modify VLANs but the changes affect
only the individual switch.
When you make a change to the VLAN configuration on a VTP server, the change is propagated to all
network devices in the VTP domain. VTP advertisements are transmitted out all trunk connections,
including Inter-Switch Link (ISL), IEEE 802.1Q, IEEE 802.10, and ATM LAN Emulation (LANE).
VTP maps VLANs dynamically across multiple LAN types with unique names and internal index
associations. Mapping eliminates excessive device administration required from network administrators.

Understanding VTP Modes

You can configure a Catalyst 6500 series switch to operate in any one of these VTP modes:
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Catalyst 6500 series switches automatically change from VTP server mode to VTP client mode if the
Note
switch detects a failure while writing configuration to NVRAM. If this happens, the switch cannot be
returned to VTP server mode until the NVRAM is functioning.

Understanding VTP Advertisements

Each network device in the VTP domain sends periodic advertisements out each trunking LAN port to a
reserved multicast address. VTP advertisements are received by neighboring network devices, which
update their VTP and VLAN configurations as necessary.
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Server—In VTP server mode, you can create, modify, and delete VLANs and specify other
configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP
servers advertise their VLAN configuration to other network devices in the same VTP domain and
synchronize their VLAN configuration with other network devices based on advertisements received
over trunk links. VTP server is the default mode.
Client—VTP clients behave the same way as VTP servers, but you cannot create, change, or delete
VLANs on a VTP client.
Transparent—VTP transparent network devices do not participate in VTP. A VTP transparent
network device does not advertise its VLAN configuration and does not synchronize its VLAN
configuration based on received advertisements. However, in VTP version 2, transparent network
devices do forward VTP advertisements that they receive out their trunking LAN ports.
Chapter 8 Configuring VTP
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