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  • 1. VLAN Trunking protocol CCNA Exploration Semester 3 Chapter 430 Sep 2012 S Ward Abingdon and Witney College 1
  • 2. Topics The role of VLAN Trunking Protocol (VTP) Operation of VTP Configure VTP on switches 2 30 Sep 2012 S Ward Abingdon and Witney College
  • 3. Semester 3 LAN Design Basic Switch Wireless ConceptsVLANs STPVTP Inter-VLAN routing 330 Sep 2012 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. 4 30 Sep 2012 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. 5 30 Sep 2012 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. 6 30 Sep 2012 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. 7 30 Sep 2012 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. 8 30 Sep 2012 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. 9 30 Sep 2012 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 1030 Sep 2012 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 11 30 Sep 2012 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. 12 30 Sep 2012 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. 13 30 Sep 2012 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. 14 30 Sep 2012 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. 1530 Sep 2012 S Ward Abingdon and Witney College
  • 16. Request AdvertisementSent 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 16 30 Sep 2012 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 17 30 Sep 2012 S Ward Abingdon and Witney College
  • 18. Subset advertisementVersion Code Seq-number Domain name lengthManagement domain name (padded to 32 bytes)Configuration revision numberVLAN info field 1VLAN info field 2Etc. 18 30 Sep 2012 S Ward Abingdon and Witney College
  • 19. Subset advertisement VLAN infoVLAN-InfoInfo length Status VLAN-Type VLAN-name LenISL VLAN ID MTU size802.10 indexVLAN name (padded to multiple of 4 bytes) 1930 Sep 2012 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. 20 30 Sep 2012 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. 21 30 Sep 2012 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. 22 30 Sep 2012 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. 23 30 Sep 2012 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. 24 30 Sep 2012 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. 25 30 Sep 2012 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 26 30 Sep 2012 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. 27 30 Sep 2012 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. 28 30 Sep 2012 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? 2930 Sep 2012 S Ward Abingdon and Witney College
  • 30. The End30 Sep 2012 S Ward Abingdon and Witney College 30