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102 Cisco LAN Switching Configuration Handbook
Changing VTP Versions
VTP supports two versions. By default all switches are in VTP version 1 mode, but most
switches can support version 2 mode.
To enable VTP version 2, which is optional, enter the following commands:
(privileged) vlan database
(vlan_database)vtp v2-mode
OR
(global)vtp version 2
VTP version 2 is disabled by default. After you have enabled version 2 on one switch, all
other switches in the domain also begin to operate in version 2 mode.
Note The global configuration command vtp version 2 is not supported on all switches
that run the IOS.
VTP version 2 offers the following support options not available with version 1:
■
Unrecognized type-length-value (TLV) support: A VTP server or client propagates
configuration changes to its other trunks, even for TLVs it cannot parse. The unrecog-
nized TLV is saved in 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. Because only one domain is supported
in the Supervisor engine software, VTP version 2 forwards VTP messages in trans-
parent 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
command-line interface (CLI) or Simple Network Management Protocol (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.
Verifying VTP Operation
After configuring VTP, use the following command to verify the VLAN port assignments:
(privileged) show vtp status
VLANs back, use the command set vtp pruneeligible vlanlist for IOS switches
or switchport trunk pruning vlan add vlanlist for IOS.
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