This document discusses the VLAN Trunking Protocol (VTP). VTP allows network managers to centrally manage VLAN configurations across multiple switches in a domain. It maintains consistency by propagating VLAN changes between switches. The document covers VTP domains, advertisements, modes, pruning, configuration and troubleshooting.

1. LAN Switching and Wireless
VTP
Abdelkhalik Mosa

2. Note !
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Thanks,
Abdelkhalik Elsaid Mosa
Suez Canal University
Faculty of Computers and Informatics - Ismailia - Egypt

3. What is VTP
• VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that
allows a network manager to configure a switch so that it will
propagate VLAN configurations to other switches in the network.

4. What is VTP
• VTP maintains VLAN configuration consistency by managing the
addition, deletion, and renaming of VLANs across multiple Cisco
switches in a network.
VTP advertisements will not be exchanged if the trunk between the switches is inactive.

5. VTP Components: VTP Domain
• VTP Domain: Consists of one or more interconnected switches.
 All switches in a domain share VLAN configuration details using VTP
advertisements.
 A router or Layer 3 switch defines the boundary of each domain.

6. VTP Components: VTP Advertisements
• VTP Advertisements: VTP uses a hierarchy of advertisements to
distribute and synchronize VLAN configurations across the
network.

7. VTP Components: VTP Modes
• VTP Modes: A switch can be configured in one of three modes:
server, client, or transparent.

8. VTP Components: VTP Modes
• VTP Server: advertises the VTP domain VLAN information to
other VTP-enabled switches in the same VTP domain.
 VTP servers store the VLAN information for the entire domain in NVRAM.
 The server is where VLANs can be created, deleted, or renamed for the
domain.
• VTP Client: functions the same way as VTP servers, but you
cannot create, change, or delete VLANs on a VTP client.
 A VTP client only stores the VLAN information for the entire domain while
the switch is on, a switch reset deletes the VLAN information.
• VTP Transparent: forwards VTP advertisements to VTP clients
and VTP servers.
 Transparent switches do not participate in VTP. VLANs that are created,
renamed, or deleted on transparent switches are local to that switch only.

9. VTP Components: VTP Pruning
• VTP Pruning: increases network available bandwidth by
restricting flooded traffic to those trunk links that the traffic
must use to reach the destination devices.

10. Relax and Refresh

11. Default VTP Configuration
S# show vtp status

12. VTP Domains
• VTP allows you to separate your network into smaller management domains
to help reduce VLAN management.
• VTP domains limit the extent to which configuration changes are propagated
in the network if an error occurs.
• A switch can be a member of only one VTP domain at a time.
• Until the VTP domain name is specified you cannot create or modify VLANs on
a VTP server, and VLAN information is not propagated over the network.

13. VTP Advertisements
• VTP advertisements (or messages) distribute VTP domain name
and VLAN configuration changes to VTP-enabled switches.
• VTP Header generally contains: Domain name, Domain name
length, version, Message type, and revision number

14. VTP Message Contents

15. VTP Revision Number
• The configuration revision number is a 32-bit number that
indicates the level of revision for a VTP frame.
 The default configuration number for a switch is zero.
 Each time a VLAN is added or removed, the configuration revision number
is incremented.
 Changes in VTP domain name, resets the revision number to zero.

16. Types of VTP advertisements: Summary Advertisement
• The summary advertisement contains the VTP domain name, the
current revision number, and other VTP configuration details.

17. Types of VTP advertisements: Subset Advertisement
• A subset advertisement contains VLAN information.

18. Types of VTP advertisements: Request Advertisement
• When a request advertisement is sent to a VTP server in the
same VTP domain, the VTP server responds by sending a
summary advertisement and then a subset advertisement.

19. Summary details
• Version: Displays the VTP version, on Catalyst 2960 v1 or v2.
• Code: Identifies the type of advertisement ‘0X01’.
• Followers: Identifies that this packet is followed by a subset advertisement.
• MgmtD Len: The length of domain name.
• Management Domain Name: The domain name.
• Configuration Rev. num.: The Rev. Num. of the VTP server sending the msg.
• Updater Identity: the IP add. Of the switch that is the last to have incremented the
configuration revision.
• Update Timestamp: Date & time of the last increment of the configuration revision.
• MD5 Digest: carries the VTP Password.

20. Subset details
• Version: Displays the VTP version, on Catalyst 2960 v1 or v2.
• Code: Identifies the type of advertisement, “0x02”.
• Seq-Number: The sequence of the packet in the stream of packets that follow a
summary advertisement, starts with 1.
• MgmtD Len: The length of domain name.
• Management Domain Name: The domain name.
• Configuration Rev. num.: The Rev. Num. of the VTP server sending the msg.

21. Request details
• Version: Displays the VTP version, on Catalyst 2960 v1 or v2.
• Code: Identifies the type of advertisement, “0x03”.
• Rsvd: A reserved field.
• MgmtD Len: The length of domain name.
• Management Domain Name: The domain name.
• Start Value: is used when there are several subset advertisements.

22. VTP Modes
• Cannot create, change,
or delete VLANs
• Forwards
advertisements after
taking a copy.
• Not saved in
NVRAM
•Creates VLANs
•Modifies VLANs
•Deletes VLANs
•Sends and forwards advertisements
•Saved in NVRAM
•Default mode
•Creates local VLANs only
•Modifies local VLANs only
•Deletes local VLANs only
•Doesn’t advertise local
configuration.
•Sends and forwards
advertisements without being
affected
•Saved in NVRAM

23. VTP in Action

24. VTP in Action

25. VTP in Action

26. VTP in Action

27. VTP in Action

28. VTP in Action

29. VTP in Action

30. VTP in Action

31. VTP in Action

32. VTP in Action

33. VTP Pruning
• VTP pruning prevents unnecessary flooding of broadcast
information from one VLAN across all trunks in a VTP domain.

34. VTP Configuration
• scu_fci# show vtp status
• scu_fci# conf t
• scu_fci(config)# vtp domain <domain-name>
• scu_fci(config)# vtp mode [ server | client | transparent ]
• scu_fci(config)# vtp version <I or 2>
• scu_fci(config)# vtp password <password>
• scu_fci# show vtp counters
Troubleshooting VTP Connections

35. Troubleshooting VTP Connections: Incompatible VTP Versions

36. Troubleshooting VTP Connections: Incorrect VTP Domain Name

37. Troubleshooting VTP Connections: Switches Set to VTP Client Mode

38. Troubleshooting VTP Connections: Incorrect Revision Number

39. Managing VLANs on a VTP Server