Cisco Catalyst 4500 series Administration Manual page 560

VLAN Trunking Protocol
Catalyst 4500 series switches do not support Token Ring or FDDI media. The switch does not forward
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FDDI, FDDI-Net, Token Ring Concentrator Relay Function (TrCRF), or Token Ring Bridge Relay
Function (TrBRF) traffic, but it does propagate the VLAN configuration by using VTP.
VTP version 2 supports the following features, which are not supported in version 1:
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VTP Version 3
VTP version 3 supports the following features not supported in version 1 or version 2:
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Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
16-10
Token Ring support—Supports Token Ring LAN switching and VLANs (TrBRF and TrCRF).
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.
Version-dependent transparent mode—In VTP version 1 and version 2, a VTP transparent network
device 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.
Hidden password support—Supports the option of configuring the password as hidden or secret.
When the hidden keyword is specified, that password must be reentered if a takeover command is
issued in the domain. The secret key generated from the password string is saved in the
const_nvram:vlan.dat file. When configured with this option, the password does not appear in plain
text in the configuration. Instead, the secret key associated with the password is saved in
hexadecimal format in the running configuration. If the hidden keyword is not specified, the
password is saved in clear text in the const_nvram:vlan.dat file as in VTP version 1 and VTP
version 2.
When the secret keyword is specified, the password secret key can be directly configured.
Extended VLAN database propagation support—In VTP version 2, VLAN configuration
information is propagated only for VLANs numbered 1 to 1000. In VTP version 3, information also
is propagated for extended-range VLANs (VLANs numbered 1006 to 4094).
On Catalyst 4500 series switches running VTP version 1, VTP version 2, or VTP version 3, default
VLANs 1 and 1002 to 1005 cannot be modified.
VTP pruning continues to apply only to VLANs numbered 1 to 1000.
Propagation of any database in a domain—In addition to propagating VLAN database information,
VTP can propagate Multiple Spanning Tree (MST) protocol database information.
Disabling VTP—When VTP is disabled on a trunking port, it applies to all VTP instances on that
port. When VTP is disabled globally, the setting applies to all the trunking ports in the system.
In VTP version 1 and VTP version 2, the role of a VTP server is to back up the database to NVRAM
and to allow the administrator to change database information. VTP version 3 introduces the roles
of VTP primary server and VTP secondary server. A VTP primary server is used to update the
Chapter 16 Configuring VLANs, VTP, and VMPS
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