Understanding Vtp Advertisements; Understanding Vtp Version 2; Understanding Vtp Pruning - Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual

Chapter 11 Configuring VTP

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.
The following global configuration information is distributed in VTP advertisements:
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Understanding VTP Version 2

If you use VTP in your network, you must decide whether to use VTP version 1 or version 2.
If you are using VTP in a Token Ring environment, you must use version 2.
Note
VTP version 2 supports the following features not supported in version 1:
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Understanding VTP Pruning

VTP pruning enhances network bandwidth use by reducing unnecessary flooded traffic, such as
broadcast, multicast, unknown, and flooded unicast packets. VTP pruning increases available bandwidth
by restricting flooded traffic to those trunk links that the traffic must use to access the appropriate
network devices. By default, VTP pruning is disabled.
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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 maximum transmission unit (MTU) size for each VLAN
Frame format
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 the
page 12-1.
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 network device
inspects VTP messages for the domain name and version, and forwards a message only if the version
and domain name match. Because only one domain is supported in the supervisor engine software,
VTP version 2 forwards VTP messages in transparent mode without checking the version.
Consistency Checks—In VTP version 2, VLAN consistency checks (such as VLAN names and
values) are performed only when you enter new information through the CLI or SNMP. Consistency
checks are not performed when new information is obtained from a VTP message, or when
information is read from NVRAM. If the digest on a received VTP message is correct, its
information is accepted without consistency checks.
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
Understanding How VTP Works
"Understanding How VLANs Work" section on
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