Vtp Version 2; Vtp Pruning - Cisco WS-C3550-12G Software Configuration Manual

Using the VLAN Trunking Protocol

VTP Version 2

If you use VTP in your network, you must decide whether to use version 1 or version 2.
VTP version 2 supports these features not supported in version 1:
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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 on Catalyst 3550 trunk ports. If the VLANs are configured
as pruning-ineligible, the flooding continues. VTP pruning is supported with VTP version 1 and
version 2.
Figure 9-2
Switch 4 are assigned to the Red VLAN. If a broadcast is sent from the host connected to Switch 1,
Switch 1 floods the broadcast and every switch in the network receives it, even though Switches 3, 5,
and 6 have no ports in the Red VLAN.
Catalyst 3550 Multilayer Switch Software Configuration Guide
9-6
Token Ring support—VTP version 2 supports Token Ring Bridge Relay Function (TrBRF) and
Token Ring Concentrator Relay Function (TrCRF) VLANs. For more information about Token Ring
VLANs, see the "VLANs in the VTP Database" section on page
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 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. 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, the Cluster
Management Software (CMS), 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 MD5
digest on a received VTP message is correct, its information is accepted.
shows a switched network without VTP pruning enabled. Port 1 on Switch 1 and Port 2 on
Chapter 9 Creating and Maintaining VLANs
9-15.
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