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VLANs

VLANs. Module 2. VLANs Trunking VLAN Trunking Protocol (VTP). VLANs. VLANs. VLANs and Physical Boundaries. VLANs. Virtual LANs segment a switched network based on Organisation function, project teams, applications (end-to-end) Or Geographic, location (local vlans)

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VLANs

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  1. VLANs Module 2

  2. VLANs Trunking VLAN Trunking Protocol (VTP) VLANs

  3. VLANs

  4. VLANs and Physical Boundaries

  5. VLANs • Virtual LANs segment a switched network based on • Organisation function, project teams, applications (end-to-end) • Or Geographic, location (local vlans) • Reconfiguration through software • Broadcast domain existing within a defined no. of switches

  6. VLANs control broadcasts

  7. When NOT to VLAN

  8. When scaling VLANs in the switch block, there are two basic methods of defining the VLAN boundaries: End-to-end VLANs (no longer recommended by Cisco due to management and STP concerns , goal is maintain 80% of traffic on end-to-end VLAN, old 80/20 rule) Local VLANs (generally geographic in nature – follow the 20/80 rule) Types of VLANs

  9. End to End VLANs

  10. End-to-End VLANs

  11. Local/Geographical VLANs

  12. VLAN Types The two common approaches to assigning VLAN Membership are: • Static VLANs • Port based – VLAN assigned to port • Dynamic VLANs • Created & controlled via S/W packages CW2000, VLAN Management Policy Server VMPS

  13. Static VLANs

  14. Dynamic VLAN

  15. CIS-2900-ServerFarm>show vlan VLAN Name Status Ports ---- -------------------------------- --------- ----------------- 1 default active 2 VLAN0002 active 3 VLAN0003 active 4 VLAN0004 active 5 VLAN0005 active 10 VLAN0010 active 50 SeverFarm active Fa0/1, Fa0/2, Fa0/3, Fa0/4, Fa0/5, Fa0/6, Fa0/7, Fa0/8, <output omitted) Fa0/21, Fa0/22 1002 fddi-default active <text omitted> VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2 ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------ 1 enet 100001 1500 - - - - - 0 0 <Text omitted> show vlan

  16. CIS-2900-ServerFarm>show vlan brief VLAN Name Status Ports ---- -------------------------------- --------- ----------------- 1 default active 2 VLAN0002 active 3 VLAN0003 active 4 VLAN0004 active 5 VLAN0005 active 10 VLAN0010 active 50 SeverFarm active Fa0/1, Fa0/2, Fa0/3, Fa0/4, Fa0/5, Fa0/6, Fa0/7, Fa0/8, <output omitted) Fa0/21, Fa0/22 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active show vlan brief

  17. Switch# show running-config ! interface FastEthernet0/1 switchport access vlan 50 ! interface FastEthernet0/2 switchport access vlan 50 ! interface FastEthernet0/3 switchport access vlan 50 ! interface FastEthernet0/4 switchport access vlan 50 show run

  18. VLANs Trunking VLAN Trunking Protocol (VTP) VLANs

  19. Trunking

  20. Access and Trunk Links

  21. Trunk Links Without trunking With trunking

  22. Standard NIC cards and networking devices don’t understand this giant frame. A Cisco switch must remove this encapsulation before sending the frame out on an access link. ISL (Frame Encapsulation) Ethernet Frame1500 bytes plus 18 byte header (1518 bytes)

  23. 2-byte TPID 2-byte TCI 802.1q NIC cards and networking devices can understand this “baby giant” frame (1522 bytes). However, a Cisco switch must remove this encapsulation before sending the frame out on an access link. SA and DA MACs SA and DA MACs 802.1q Tag Type/Length Field Data (max 1500 bytes) CRC NewCRC Tag Protocol Identifier Tag Control Info (includes VLAN ID)

  24. Before attempting to configure a VLAN trunk on a port, you should to determine what encapsulation the port can support. switch(config-if)# switchport trunk encapsulation ? Trunking

  25. A trunk is a point-to-point link between: Two switches A switch and a router Trunks carry traffic of multiple VLANs Cisco supports one or both of these Trunking protocols: IEEE 802.1Q (dot1q) ISL (Cisco proprietary) Trunking

  26. Switch(config)# interfacefastethernet 0 Switch(config-if)# switchport mode [access | multi | trunk] Switch(config-if)# switchport trunk encapsulation {isl|dot1q} Switch(config-if)# switchport trunk allowed vlan remove vlan-list Switch(config-if)# switchport trunk allowed vlan add vlan-list By default, all VLANS, 1-1005 transported automatically Configuring Trunking

  27. interface FastEthernet0/1.1 encapsulation dot1Q 1 ip address 172.30.1.1 255.255.255.0 ip access-group 100 in ip helper-address 172.30.50.50 no ip directed-broadcast ! interface FastEthernet0/1.2 encapsulation dot1Q 2 ip address 172.30.2.1 255.255.255.0 ip access-group 102 in ip helper-address 172.30.50.255 ip helper-address 172.30.50.10 no ip directed-broadcast Router

  28. VLANs Trunking VLAN Trunking Protocol (VTP) VLANs

  29. VTP

  30. VLAN Trunking Protocol • VTP maintains VLAN configuration consistency across the entire network. • VTP is a messaging protocol that uses Layer 2 trunk frames to manage the addition, deletion, and renaming of VLANs on a network-wide basis. • Further, VTP allows you to make centralized changes that are communicated to all other switches in the network.

  31. Create VLANs on the VTP Server Those VLANs get sent to other client switches On the client switches, you can now assign ports to those vlans. Cannot create vlans on the client switches like you could previously before configuring the switch to be a VTP client. VTP

  32. All switches in the same management domain share their VLAN information with each other, and a switch can participate in only one VTP management domain. Switches in different domains do not share VTP information. Using VTP, switches advertise: Management domain Configuration revision number Known VLANs and their specific parameters VTP

  33. Switches can be configured not to accept VTP information. These switches will forward VTP information on trunk ports in order to ensure that other switches receive the update, but the switches will not modify their database, nor will the switches send out an update indicating a change in VLAN status. This is referred to as transparent mode. VTP

  34. By default, management domains are set to a nonsecure mode, meaning that the switches interact without using a password. Adding a password automatically sets the management domain to secure mode. A password must be configured on every switch in the management domain to use secure mode. VTP

  35. VTP • The VTP database contains a revision number. • Each time a change is made, the switch increments the revision number

  36. A higher configuration revision number indicates that the VLAN information that is being sent is more current then the stored copy. Any time a switch receives an update that has a higher configuration revision number, the switch will overwrite the stored information with the new information being sent in the VTP update. VTP

  37. VTP Modes • Switches can operate in any one of the following three VTP modes: • Server • Client • Transparent

  38. Server - If you configure the switch for server mode, you can create, modify, and delete VLANs, and specify other configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP servers: advertise their VLAN configuration to other switches in the same VTP domain synchronize the VLAN configuration with other switches based on advertisements received over trunk links. Recommended you have at least 2 VTP servers in case one goes down This is the default mode on the switch. VTP Modes

  39. VTP Modes • Client- VTP clients behave the same way as VTP servers. However, you cannot create, change, or delete VLANs on a VTP client.

  40. VTP Modes • Transparent - VTP transparent switches do not participate in VTP. • A VTP transparent switch does not advertise its VLAN configuration, and does not synchronize its VLAN configuration based on received advertisements. • However, in VTP Version 2, transparent switches do forward VTP advertisements that the switches receive out their trunk ports.

  41. Switch# vlan database Switch(vlan)# vtp domain domain-name Switch(vlan)# vtp {server | client | transparent} Optional: Switch(vlan)# vtp password password Switch(vlan)# vtp v2-mode (version2) Example: ALSwitch# vlan database ALSwitch(vlan)# vtp domain corp ALSwitch(vlan)# vtp client Configuring VTP

  42. VLANs Trunking VLAN Trunking Protocol (VTP) Summary

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