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Efficient Inter-VLAN Routing Methods | Networking Guide

Learn about traditional, router-on-a-stick, and switch-based Inter-VLAN routing methods for seamless communication between VLANs in a network. Understand the concepts, configurations, and benefits of each approach.

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Efficient Inter-VLAN Routing Methods | Networking Guide

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  1. Chapter 6 Inter-VLAN Routing

  2. Inter-VLAN Routing Introducing Inter-VLAN Routing

  3. Introducing Inter-VLAN Routing • What is Inter-VLAN Routing? • Each VLAN is a unique broadcast domain. • Computers on separate VLANs are, by default, not able to communicate. • Each VLAN is a unique IP subnetwork. • To allow VLANs to communicate, we need a router to communicate among separate broadcast domains and unique IP subnetworks. • Inter-VLAN routing, then, is a process of forwarding traffic from one VLAN to another VLAN using a router.

  4. Introducing Inter-VLAN Routing • Methods: • Traditional Inter-VLAN Routing. • Router-on-a-stick Inter-VLAN Routing. • Switch Based Inter-VLAN Routing.

  5. Introducing Inter-VLAN Routing Internally Routed to the proper subnet. • Traditional Inter-VLAN Routing: • One router interface per VLAN. VLAN Tagged Tagremoved

  6. Introducing Inter-VLAN Routing Internally Routed to the proper subnet. • Router-on-a-stick Inter-VLAN Routing: • One router interface for all VLANs. VLAN Tagged Tagremoved

  7. Introducing Inter-VLAN Routing • Layer 3 Switch Inter-VLAN Routing: • Uses Switch Virtual Interfaces (SVI) to retagthe frame. Tagremoved VLAN Tagged (10)

  8. Interfaces and Subinterfaces • Traditional Inter-VLAN Routing: • Traditional routing requires routers to have multiple physical interfaces to facilitate inter-VLAN routing. • Each interface is also configured with an IP address for the subnet associated with the particular VLAN that it is connected to. • In this configuration, network devices can use the router as a gateway to access the devices connected to the other VLANs.

  9. Interfaces and Subinterfaces Router tagsthe framefor VLAN 30 And switches itto Port F0/1. Router Responds Traditional Inter-VLAN Routing Routing table: 172.17.10.0 – F0/0 172.17.30.0 – F0/1 Tagged VLAN 10 Tag Removed

  10. Interfaces and Subinterfaces Traditional Inter-VLAN Routing

  11. Interfaces and Subinterfaces • Traditional Inter-VLAN Routing: • Traditional inter-VLANrouting using physicalinterfaces does have alimitation. • As the number of VLANsincreases on a network, thephysical approach of having one router interface per VLAN quickly becomes hindered by the physical hardware limitations of a router. • Routers have a limited number of physical interfaces that they can use to connect to different VLANs. • It is very expensive to add an Ethernet Interface.

  12. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Subinterfaces: • Overcomes the hardware limitation of a router. • Subinterfaces are software-based virtual interfaces that are assigned to physical interfaces. • Each subinterface is configured with its own IP address, subnet mask, and unique VLAN assignment. • Connected to a switch trunk link. • Functionally the same as using the traditional routing model.

  13. Interfaces and Subinterfaces Router-on-a-stick Inter-VLAN Routing Routing table: 172.17.10.0 – F0/0.10 172.17.30.0 – F0/0.30 TaggedVLAN 30 TaggedVLAN 10 TagRemoved TagRemoved TaggedVLAN 30 TagRemoved

  14. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Configuring Subinterfaces: • Similar to configuring physical interfaces. • Create the subinterface. • Assign it to a VLAN. • Assign an IP Address. • Enable the interface.

  15. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Create the subinterface: • The syntax for the subinterface is always the physical interface, followed by a period and a subinterface number. • The subinterface number is configurable, but it is typically associated to reflect the VLAN number. R1(config)#interface[interface].nnNOTE: The management VLAN must also be configured if you wish to use it on multiple switches that are not directly connected by trunk links.

  16. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Assign it to a VLAN: • Before assigning an IP Address, the interface must to be configured to operate on a specific VLAN using the proper encapsulation. R1(config-subif)#encapsulation dot1qvlan-id

  17. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Assign an IP Address: • The IP Address assigned here will become the default gateway for that VLAN. R1(config-subif)#ip address [address] [mask]

  18. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Enable the interface: • Subinterfaces are not enabled individually. • When the physical interface is enabled, all associatedsubinterfaces are enabled. R1(config-if)#no shutdown

  19. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Configuring Subinterfaces: VLAN 10 VLAN 10 VLAN 10 VLAN 30 VLAN 30 Enable Interfaces

  20. Interfaces and Subinterfaces • Router-on-a-stick Inter-VLAN Routing: • Configuring Subinterfaces: Planning!

  21. Interfaces and Subinterfaces • Router Interface and Subinterface Comparison:

  22. Inter-VLAN Routing Configuring Inter-VLAN Routing (Putting It All Together)

  23. Configuring Inter-VLAN Routing • Traditional Inter-VLAN Routing:

  24. Configuring Inter-VLAN Routing • Traditional Inter-VLAN Routing:

  25. Configuring Inter-VLAN Routing • Traditional Inter-VLAN Routing:

  26. Configuring Inter-VLAN Routing • Router-on-a-stick Inter-VLAN Routing: VLANs Trunk in Native VLAN Trunk Interfaces VLANs

  27. Configuring Inter-VLAN Routing • Router-on-a-stick Inter-VLAN Routing: VLAN 10 VLAN 30 Enable All Subinterfaces

  28. Inter-VLAN Routing Troubleshooting Inter-VLAN Routing

  29. Configuring Inter-VLAN Routing VLAN 30 is working but VLAN 10 cannot communicate with the router or VLAN 30. • Switch Configuration Issues: Interface F0/4 is still in the default VLAN. switchport access vlan 10

  30. Configuring Inter-VLAN Routing Each of the configured subinterfaces is unable to send or receive VLAN traffic. • Switch Configuration Issues: Interface F0/5 is still in the default VLAN. switchport mode trunk

  31. Configuring Inter-VLAN Routing PC1 cannot communicate with the router interface and the router cannot route to VLAN 30. • Router Configuration Issues: Switch port F0/4 is for VLAN 10. Switch port F0/9 is assigned to the default VLAN. Move the cable from F0/9 to F0/4. Move the cable from F0/9 to F0/4. One of the most common mistakes in Inter-VLAN routing.

  32. Configuring Inter-VLAN Routing PC1 cannot communicate with the router interface and the router cannot route to VLAN 30. • Router Configuration Issues:

  33. Configuring Inter-VLAN Routing PC1 cannot communicate. • IP Addressing Issues: Incorrect IP address for subnet 172.16.10.0/24. Incorrect subnet mask for subnet 172.16.10.0/24. Incorrect IP address for subnet 172.16.10.0/24.

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