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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter13 Configuring VTP
Understanding VTP
•Update identity and update timestamp
•MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each
VLAN.
•Frame format
VTP advertisements distribute this VLAN information for each configured VLAN:
•VLAN IDs (IEEE 802.1Q)
•VLAN name
•VLAN type
•VLAN state
•Additional VLAN configuration information specific to the VLAN type
VTP Version 2
If you use VTP in your network, you must decide whether to use Version 1 or Version 2. By default, VTP
operates in Version 1.
VTP Version 2 supports these features that are not supported in Version1:
•Token Ring support—VTP Version2 supports Token Ring Bridge Relay Function (TrBRF) and
Token Ring Concentrator Relay Function (TrCRF) VLANs. For more information about Token Ring
VLANs, see the “Configuring Normal-Range VLANs” section on page 12-4.
•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 when the switch is operating in VTP server mode.
•Version-Dependent Transparent Mode—In VTP Version1, a VTP transparent switch inspects VTP
messages for the domain name and version and forwards a message only if t he version and domain
name match. Because VTP Version 2 supports only one domain, it forwards VTP messages in
transparent mode without inspecting the version and domain name.
•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 f rom a VTP message or when
information is read from NVRAM. If the MD5 digest on a received VTP message is correct, its
information is accepted.
VTP Pruning
VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links
that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods
broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even
though receiving switches might discard them. VTP pruning is disabled by default.
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the
pruning-eligible list. Only VLANs included in the pruning-eligible list can be pruned. By default,
VLANs 2 through 1001 are pruning eligible switch trunk por ts. If the VLANs are configured as
pruning-ineligible, the flooding continues. VTP pruning is supported with VTP Version 1 and Version2.