Cisco Catalyst 4500 Series, Software Configuration Manual

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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 17 Configuring VLANs, VTP, and VMPS
VLAN Trunking Protocol
These sections describe how VTP works:
• Understanding the VTP Domain, page 17-8
•
Understanding VTP Modes, page 17-8
• Understanding VTP Advertisements, page 17-9
•
Understanding VTP Versions, page 17-9
• Understanding VTP Pruning, page 17-10
Understanding the VTP Domain
A VTP 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 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 4500 series switch is in VTP server mode and the domain is set to NULL until
the switch receives an advertisement for a domain over a trunk link or you configure a management
domain. You cannot create or modify VLANs on a VTP server until the management domain name is
specified or learned.
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 Inter-Switch Link (ISL)
and IEEE 802.1Q trunk connections.
VTP maps VLANs dynamically across multiple LAN types with unique names and internal index
associations. Mapping eliminates unnecessary device administration for network administrators.
Understanding VTP Modes
You can configure a Catalyst 4500 series switch to operate in any one of these VTP modes:
•
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.
Note
In VTP version 3, manipulation of VLANs can be done only to primary servers.
•
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 on their trunking LAN interfaces.