VLAN Trunking protocol

1. VLAN Trunking protocol CCNA Exploration Semester 3 Chapter 4 S Ward Abingdon and Witney College

2. Topics • The role of VLAN Trunking Protocol (VTP) • Operation of VTP • Configure VTP on switches S Ward Abingdon and Witney College

3. LAN Design Basic Switch Concepts Wireless VLANs STP Inter-VLAN routing VTP Semester 3 S Ward Abingdon and Witney College

4. Purpose of VTP • You can create VLANs on a switch. • What if you have the same VLANs on 10 linked switches? Or 100 linked switches? • Do you have to create the VLANs on every switch and allow them on each trunk? • VTP helps. • But you still have to assign access ports to VLANs on each switch. S Ward Abingdon and Witney College

5. VTP domain • Group of layer 2 switches sharing VLAN data. • Ends at router or layer 3 switch. • Switch can be linked but not part of domain. • Each switch can belong to only one domain. • Domain is defined by its name. • Proprietary to Cisco, so all switches in domain must be Cisco switches. S Ward Abingdon and Witney College

6. VTP server • One switch acts as server. • Create VLANs on this switch. • Information saved in vlan.dat. • Server sends VLAN information to client switches over active trunk links. • Add, delete, rename VLANs on server. • Default mode of switch is server. S Ward Abingdon and Witney College

7. VTP client • Client receives VLAN information from server. • Client switches then have the same VLANs as the server. • Client does not save VLAN information. It is held only in RAM and lost if switch is powered off. S Ward Abingdon and Witney College

8. VTP modes • Server – default mode. Sends VLAN information to other switches. • Client – receives VLAN information and forwards it to other switches. • Transparent – forward VTP traffic but do not originate or use it. They can have their own VLANs, not shared with other switches. S Ward Abingdon and Witney College

9. VTP defaults • Version 1. (Versions 2 and 3 also exist.) • VTP domain name is not set. • VTP mode server • One active VLAN, VLAN 1 • Configuration revision number 0 • Any switches added to a domain should be in the default condition or they may send unwanted information to other switches. S Ward Abingdon and Witney College

10. Show vtp status • VTP Version • Maximum VLANs Supported • Number of Existing VLANs • VTP Operating Mode- server, client, or transparent. • VTP Domain Name • VTP Pruning Mode • VTP V2 Mode (disabled by default) • VTP Traps Generation • MD5 Digest (checksum of VTP configuration) • Configuration Last Modified S Ward Abingdon and Witney College

11. VTP advertisements • Consist of VTP header and VTP message • Encapsulated inside Ethernet frame with tag to pass over trunk link. • Destination MAC address is multicast address 01-00-0C-CC-CC-CC S Ward Abingdon and Witney College

12. VTP message header • Domain name • Domain name length • Version - VTP 1 or VTP 2, on Cisco 2960 switch. • Configuration revision number • Other fields, depending on type of message. S Ward Abingdon and Witney College

13. Configuration revision number • 32-bit number. • Default value is 0. • It is incremented each time a VLAN is added or removed. • Reset to 0 is domain name changes. • Switch uses it to see if information is more recent that what it already holds. S Ward Abingdon and Witney College

14. Summary advertisement • Sent immediately after a change is made, with updated revision number. • Sent every 5 minutes by servers and clients to check on current VTP configuration revision number. • Contains the VTP domain name, the current revision number, and other VTP configuration details. S Ward Abingdon and Witney College

15. VTP Summary advertisement • A switch receives a summary advertisement. • Compares domain name to its own domain name. • If name is different, the switch ignores the packet. • If the name is the same, the switch compares the revision number to its own revision number. • Number higher or equal, ignored the packet. • Number lower, sends an advertisement request. S Ward Abingdon and Witney College

16. Request Advertisement Sent by client to server if: • The VTP domain name has been changed • The switch receives a summary advertisement with a higher configuration revision number than its own • A subset advertisement message is missed for some reason • The switch has been reset S Ward Abingdon and Witney College

17. Subset advertisement • Contains VLAN information. Several may be needed if there is a lot of information. • Sent by server in response to a request or after: • Creating or deleting a VLAN • Suspending or activating a VLAN • Changing the name of a VLAN • Changing the MTU of a VLAN S Ward Abingdon and Witney College

18. Subset advertisement S Ward Abingdon and Witney College

19. Subset advertisement VLAN info S Ward Abingdon and Witney College

20. Pros and cons • Small network – don’t bother with VTP. • Big network – good for consistency and easier to make changes. • Server switches need lots of flash memory, clients do not. • Redundancy – don’t have everything on one server switch. • Problems from large domains. • Extreme care when adding a switch. S Ward Abingdon and Witney College

21. Why transparent? • Put a switch in transparent mode if it has local VLANs that are not on other switches. • The other switches do not need to know about them. S Ward Abingdon and Witney College

22. VTP pruning • Disabled by default • Enable it on one server in domain. • Stops VLAN traffic from being sent on links that do not lead to devices on that VLAN. • Cuts down on traffic on trunk links. S Ward Abingdon and Witney College

23. Domain names and passwords • Configure a domain name on the first server switch. The other switches will learn it. • If you configure it on other switches, check that it is exactly the same. It is case sensitive. • If you use a password then it must be exactly the same on all switches. S Ward Abingdon and Witney College

24. Versions • VTP version 1 is used by default on Catalyst switches, but they can use version 2. • If you configure version 2 on one switch then the other switches should learn the new version and change to it. • If a switch is not capable of running version 2 then it will not exchange advertisements. S Ward Abingdon and Witney College

25. Configure VTP • Configure VTP with a domain name before creating VLANs on the server. • Existing VLANs are removed when you start to configure VTP. • Check that links are trunk links. • Configure client switches to client mode. S Ward Abingdon and Witney College

26. Commands on server • SW1(config)#vtp domain cisco1 • SW1(config)#vtp password cisco • (Password is optional) • Server mode is default, but if it was changed: • SW1(config)#vtp mode server • Version 1 is default, but command is: • SW1(config)#vtp version 1 S Ward Abingdon and Witney College

27. Commands on server • Create VLANs • Check that link is a trunk. • Check VTP operation • SW1# show vtp status • Assign switch ports to VLANs. S Ward Abingdon and Witney College

28. Client configuration • SW2(config)#vtp mode client • Check that link is a trunk. • Check VTP operation • SW2# show vtp status • Assign switch ports to VLANs. S Ward Abingdon and Witney College

29. Things to check • VTP Version. It needs to be the same on all switches in the domain. • Domain name. Is it exactly the same on all switches? • VTP Password if any. Is it exactly the same on all switches? • Check that there is at least one server. Better to have at least two. • If you recently added a new switch, had its revision number been set to 0? S Ward Abingdon and Witney College

30. The End S Ward Abingdon and Witney College