Vtp Version 2; Vtp Pruning - Cisco Catalyst 2950 Software Manual

Chapter 8 Configuring VLANs
VTP advertisements distribute this VLAN information for each configured VLAN:
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VTP Version 2

VTP version 2 supports these features not supported in version 1:
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VTP Pruning

Pruning increases 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 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 2950 trunk ports. If the VLANs are configured
as pruning-ineligible, the flooding continues. VTP pruning is also supported with VTP version 1 and
version 2.
Figure 8-2
not forwarded to Switches 3, 5, and 6 because traffic for the Red VLAN has been pruned on the links
shown (port 5 on Switch 2 and port 4 on Switch 4).
78-11380-03
VLAN ID
VLAN name
VLAN type
VLAN state
Additional VLAN configuration information specific to the VLAN type
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
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
nonvolatile RAM 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 Suite, or SNMP. Consistency checks are not performed when new information is
obtained from a VTP message or when information is read from nonvolatile RAM. If the digest on
a received VTP message is correct, its information is accepted without consistency checks.
shows a switched network with VTP pruning enabled. The broadcast traffic from Switch 1 is
"VLANs in the VTP Database" section on page
Catalyst 2950 Desktop Switch Software Configuration Guide
Using VTP
8-15.
8-9