Understanding Vtp Advertisements; Understanding Vtp Version 2; Understanding Vtp Pruning - Cisco 4500M Software Manual

Chapter 27 Understanding and Configuring VTP

Understanding VTP Advertisements

Each network device in the VTP domain sends periodic advertisements out each trunking LAN interface
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.
Catalyst 4500 series switch do not support Token Ring or FDDI media. The switch does not forward
Note
FDDI, FDDI-Net, Token Ring Concentrator Relay Function [TrCRF], or Token Ring Bridge Relay
Function [TrBRF] traffic, but it does propagate the VLAN configuration via VTP.
VTP version 2 supports the following features, which are 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, and 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 (TrBRF and
TrCRF).
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.
Software Configuration Guide—Release 12.2(25)EW
Overview of VTP
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