network protocols handbook.pdf

278Protocols GuideCisco Protocolstion revision and issues a summary advertisement, followed byone or several subset advertisements. A subset advertisementcontains a list of VLAN information. If there are several VLANS,more than one subset advertisement may be required in orderto advertise them all.Subset Advert Packet Format:Version8 16 24 32bitCodeSequenceNumberMgmtD LenManagement Domain Nance (zero-padded to 32 bytes)Configuration RevisionVLAN - info field 1......................................................VLAN - info field NThe following formatted example shows that each VLAN informationfield contains information for a different VLAN (orderedwith lower valued ISL VLAN IDs occurring first):V - info - len Status VLAN - TypeISL VLAN - id802.10 indexMTU SizeVLAN - nameLenVLAN - name (padded with zeros to multiple of 4 bytes)• Code—The format for this is 0x03 for an advertisementrequest• Start Value—This is used in cases where there areseveral subset advertisements. If the first (N) subsetadvertisement has been received and the subsequentone (N+1) has not, the Catalyst only requestsadvertisements from the (N+1)th one.Related protocolsIEEE 802.1QSponsor SourceVTP is a Cisco protocol.Referencehttp://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a008019f048.html#1017196Understanding and Configuring VLAN Trunking ProtocolMost of the fields in this packet are easy to understand. Beloware two clarifications:• Code—The format for this is 0x02 for subset advertisement.• Sequence number—This is the sequence of thepacket in the stream of packets following a summaryadvertisement. The sequence starts with 1.Advertisement RequestsA switch needs a VTP advertisement request in the followingsituations:• The switch has been reset.• The VTP domain name has been changed.• The switch has received a VTP summary advertisementwith a higher configuration revision than itsown.Upon receipt of an advertisement request, a VTP device sendsa summary advertisement, followed by one or more subset advertisements.Below is an example.8 16 24 32bitVersion Code Rsvd MgmtD LenManagement Domain Nance (zero-padded to 32 bytes)Start - Value