1. CCNA 3 Week 9 VLAN Trunking

2. Copyright © 2005 University of Bolton Origins Dates back to radio and telephone Trunk carries multiple channels over a single link Single link between switches carrying multiple VLANS

3. Copyright © 2005 University of Bolton Lan Trunking Trunking saves ports and reduces wiring between switches Removes complexity from physical hardware

4. Copyright © 2005 University of Bolton Trunking Operation Need a method to identify which frames are destined for each subnet/VLAN –Filtering –Tagging

5. Copyright © 2005 University of Bolton IEEE 802.1Q Switches need to be able to determine which VLAN frames from a trunk should be passed to Cisco offers Propriatary ISL or 802.1Q 802.1Q protocol includes VLAN tagging as part of layer 2 frames Standard protocol used by many manufacturers

6. Copyright © 2005 University of Bolton Frame Tagging Frames have a VLAN id inserted into Frame header Understood and read by switches VLAN identifier removed before traffic leaves trunked/backbone links

7. Copyright © 2005 University of Bolton Setup Trunking Commands to enable trunking Sw1(config)# interface fastethernet0/1 Sw1(config-if)# switchport mode trunk Sw1(config-if)# switchport trunk encapsulation dot1q Sw1(config-if)# end Naturally need to enable trunking at each end of a trunked link

8. VLAN Trunking Protocol

9. Copyright © 2005 University of Bolton History of VTP Protocol created by Cisco Need consistency in VLAN numbering to allow trunking across large network Either have to manage each switch individually Manage centrally to ensure consistency Otherwise risk cross-connection or failure to pass on frames

10. Copyright © 2005 University of Bolton VTP Concepts VTP uses layer 2 trunk frames to Add, Delete and Rename VLANs VTP messages encapsulated in ISL or 802.1q

11. Copyright © 2005 University of Bolton VTP Messages Contain the following –VTP protocol version - Either version 1 or 2 –VTP message type - Indicates one of four types of messages –Management domain name length - Indicates the size of the name that follows –Management domain name - Name configured for the management domain

12. Copyright © 2005 University of Bolton VTP Modes VLAN Server –Can create/modify/delete vlans for entire domain –Save VLAN config in NVRAM –Send VTP messages to all trunk ports VLAN Client –Cannot make changes –Record information and forward VTP messages Transparent Mode –Forward Messages but ignore content –Can create local VLANs

13. Copyright © 2005 University of Bolton VTP Implementation Each switch advertises multicasts via trunk ports –its management domain –configuration revision number –the VLANs that it knows about Clients request info at bootup, servers respond

14. Copyright © 2005 University of Bolton Summary Advertisements Sent every five minutes with current VTP revision number If greater that the receiver's revision number, an advertisement request is sent

15. Copyright © 2005 University of Bolton Subset Advertisements Subset advertisements contain detailed information about VLANs –VTP version type –Domain name –Configuration revision number. Certain actions can trigger subset advertisements: –VLAN creation or deletion –VLAN suspension or activation –VLAN name change –VLAN maximum transmission unit (MTU) change

16. Copyright © 2005 University of Bolton Advertisement Contents Management domain name - Advertisements with different names are ignored. Configuration revision number - The higher number indicates a more recent configuration. Message Digest 5 (MD5) - MD5 is the key that is sent with the VTP when a password has been assigned. If the key does not match, the update is ignored. Updater identity - The updater identity is the identity of the switch that sends the VTP summary advertisement.

17. Copyright © 2005 University of Bolton VTP Configuration Determine the version number of VTP that will be utilized. Is a new management domain needed To join an existing domain, name and password are needed Choose a VTP mode for the switch –V1 and V2 not interoperable

18. Copyright © 2005 University of Bolton VTP Commands Switch#vlan database Switch(vlan)#vtp v2-mode Switch(vlan)#vtp domain cisco Switch(vlan)#vtp {client | server | transparent}

19. Routers and VLANs

20. Copyright © 2005 University of Bolton Need for routers To pass traffic between subnets(VLANs) a router is required Segment broadcast domains Trunks may connect to router

21. Copyright © 2005 University of Bolton Routers Trunked Links Not cost effective to have dedicated ethernet port per vlan Can split physical interface into logical sub-interfaces A logical interface for each subnet

22. Copyright © 2005 University of Bolton Sub-interfaces A logical interface within a physical interface Each sub-interface has own IP address and belongs to one VLAN Denoted by FA0/1.1, FA0/1.2 etc Router passes traffic between sub-interfaces

23. Copyright © 2005 University of Bolton Sub-interface setup Router(config)#int fa port-number.subint-number Router(config-if)#encapsulation dot1q vlan-no Router(config-if)#ip address ip-address subnet-mask