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Chapter 9
Configuring VTP
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VTP Version 2
If you use VTP in your network, you must decide whether to use VTP version 1 or version 2. VTP
version 2 supports the following features not supported in version 1:
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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.
Make sure that all devices in the management domain support VTP pruning before enabling it.
Figure 9-1
Switch 4 are assigned to the Red VLAN. 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.
78-12647-02
VLAN configuration, including maximum transmission unit (MTU) size for each VLAN
Frame format
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 (NVRAM).
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. Since 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.
shows a switched network with VTP pruning disabled. Port 1 on Switch 1 and port 2 on
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
Understanding How VTP Works
9-3
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Troubleshooting
