Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 161

Chapter 11 Configuring VTP Understanding How VTP Works Understanding VTP Advertisements Each network device in the VTP domain sends periodic advertisements out each trunking LAN port to a reserved multicast address. VTP advertisements are received by neighboring network devices, which update their VTP and VLAN configurations as necessary. The following global configuration information is distributed in VTP advertisements: • VLAN IDs (ISL and 802.1Q) • Emulated LAN names (for ATM LANE) • 802.10 SAID values (FDDI) • VTP domain name • VTP configuration revision number • VLAN configuration, including maximum transmission unit (MTU) size for each VLAN • Frame format Understanding VTP Version 2 If you use VTP in your network, you must decide whether to use VTP version 1 or version 2. Note If you are using VTP in a Token Ring environment, you must use version 2. VTP version 2 supports the following features not supported in version 1: • 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 "Understanding How VLANs Work" section on page 12-1. • 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, a VTP transparent network device 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 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. Understanding 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. OL-11439-03 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY 11-3