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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 10 Configuring VTP
Understanding How VTP Version 1 and Version 2 Work
•
Transparent—VTP transparent switches do not participate in VTP. A VTP transparent switch does
not advertise its VLAN configuration and does not synchronize its VLAN configuration based on
received advertisements. However, in VTP version 2, transparent switches do forward VTP
advertisements that they receive out their trunk ports.
•
Off—In the three modes described above, VTP advertisements are received and transmitted as soon
as the switch enters the management domain state. In the VTP off mode, the switch behaves the same
as in VTP transparent mode with the exception that VTP advertisements are not forwarded.
Understanding VTP Advertisements
Each switch in the VTP domain sends periodic advertisements out each trunk port to a reserved multicast
address. VTP advertisements are received by neighboring switches, which update their VTP and VLAN
configurations as necessary.
The following global configuration information is distributed in VTP advertisements:
•
VLAN IDs (ISL and 802.1Q)
•
Emulated LAN names (for ATM LANE)
•
802.10 SAID values (FDDI)
•
VTP domain name
•
VTP configuration revision number
•
VLAN configuration, including the maximum transmission unit (MTU) size for each VLAN
•
Frame format
Understanding VTP Version 2
If you use VTP in your network, you must decide whether to use VTP version 1, version 2, or version 3
(for details on version 3, see the
“Understanding How VTP Version 3 Works” section on page 10-12
).
Note
If you are using VTP in a Token Ring environment, you must use version 2.
VTP version 2 supports the following features that are not supported in version 1:
•
Token Ring support—VTP version 2 supports Token Ring LAN switching and VLANs (Token Ring
Bridge Relay Function [TrBRF] and Token Ring Concentrator Relay Function [TrCRF]). For more
information about Token Ring VLANs, see
Chapter 11, “Configuring VLANs.”
•
Unrecognized Type-Length-Value (TLV) Support—A VTP server or client propagates configuration
changes to its other trunks even for TLVs it is not able to parse. The unrecognized TLV is saved in
NVRAM.
•
Version-Dependent Transparent Mode—In VTP version 1, a VTP transparent switch inspects VTP
messages for the domain name and version and forwards a message only if the version and domain
name match. Since only one domain is supported in the supervisor engine software, VTP version 2
forwards VTP messages in transparent mode without checking the version.