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Chapter 6 Lecture11 Inter-VLAN Routing Assistant Professor Pongpisit Wuttidittachotti, Ph.D. Faculty of Information Technology King Mongkut's University.

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Presentation on theme: "Chapter 6 Lecture11 Inter-VLAN Routing Assistant Professor Pongpisit Wuttidittachotti, Ph.D. Faculty of Information Technology King Mongkut's University."— Presentation transcript:

1 Chapter 6 Lecture11 Inter-VLAN Routing Assistant Professor Pongpisit Wuttidittachotti, Ph.D. Faculty of Information Technology King Mongkut's University of Technology North Bangkok (KMUTNB) 1

2 Chapter 6 Note for Instructors These presentations are the result of a collaboration among the instructors at St. Clair College in Windsor, Ontario. Thanks must go out to Rick Graziani of Cabrillo College. His material and additional information was used as a reference in their creation. If anyone finds any errors or omissions, please let me know at: – tdame@stclaircollege.ca. 2

3 Chapter 6 Inter-VLAN Routing Introducing Inter-VLAN Routing 3

4 Chapter 6 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

5 Chapter 6 Introducing Inter-VLAN Routing Methods: – Traditional Inter-VLAN Routing. – Router-on-a-stick Inter-VLAN Routing. – Switch Based Inter-VLAN Routing. 5

6 Chapter 6 Introducing Inter-VLAN Routing Traditional Inter-VLAN Routing: – One router interface per VLAN. VLAN Tagged Internally Routed to the proper subnet. Tag removed 6

7 Chapter 6 Introducing Inter-VLAN Routing Router-on-a-stick Inter-VLAN Routing: – One router interface for all VLANs. VLAN Tagged Internally Routed to the proper subnet. Tag removed 7

8 Chapter 6 Introducing Inter-VLAN Routing Layer 3 Switch Inter-VLAN Routing: – Uses Switch Virtual Interfaces (SVI) to retag the frame. VLAN Tagged (10) (10) Tag removed 8

9 Chapter 6 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

10 Chapter 6 Traditional Inter-VLAN Routing Interfaces and Subinterfaces Tagged VLAN 10 Tagged TagRemovedTagRemoved Router Responds Routing table: 172.17.10.0 – F0/0 172.17.30.0 – F0/1 Routing table: 172.17.10.0 – F0/0 172.17.30.0 – F0/1 Router tags the frame for VLAN 30 And switches it to Port F0/1. Router tags the frame for VLAN 30 And switches it to Port F0/1. 10

11 Chapter 6 Interfaces and Subinterfaces Traditional Inter-VLAN Routing 11

12 Chapter 6 Interfaces and Subinterfaces Traditional Inter-VLAN Routing: – Traditional inter-VLAN routing using physical interfaces does have a limitation. – As the number of VLANs increases on a network, the physical 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

13 Chapter 6 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

14 Chapter 6 Interfaces and Subinterfaces Router-on-a-stick Inter-VLAN Routing Tagged VLAN 10 Tag Removed Routing table: 172.17.10.0 – F0/0.10 172.17.30.0 – F0/0.30 Routing table: 172.17.10.0 – F0/0.10 172.17.30.0 – F0/0.30 Tagged VLAN 30 Tag Removed Tagged VLAN 30 Tag Removed 14

15 Chapter 6 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

16 Chapter 6 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].nn NOTE: 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

17 Chapter 6 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 dot1q vlan-id 17

18 Chapter 6 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

19 Chapter 6 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 associated subinterfaces are enabled. R1(config-if)#no shutdown 19

20 Chapter 6 Interfaces and Subinterfaces Router-on-a-stick Inter-VLAN Routing: – Configuring Subinterfaces: VLAN 10 VLAN 30 VLAN 10 VLAN 30 Enable Interfaces 20

21 Chapter 6 Interfaces and Subinterfaces Router-on-a-stick Inter-VLAN Routing: – Configuring Subinterfaces: Planning!Planning! 21

22 Chapter 6 Interfaces and Subinterfaces Router Interface and Subinterface Comparison: 22

23 Chapter 6 Inter-VLAN Routing Configuring Inter-VLAN Routing (Putting It All Together) 23

24 Chapter 6 Configuring Inter-VLAN Routing Traditional Inter-VLAN Routing: 24

25 Chapter 6 Configuring Inter-VLAN Routing Traditional Inter-VLAN Routing: 25

26 Chapter 6 Configuring Inter-VLAN Routing Traditional Inter-VLAN Routing: 26

27 Chapter 6 Configuring Inter-VLAN Routing Router-on-a-stick Inter-VLAN Routing: VLANsVLANs TrunkTrunk InterfacesInterfaces VLANsVLANs Trunk in Native VLAN 27

28 Chapter 6 Configuring Inter-VLAN Routing Router-on-a-stick Inter-VLAN Routing: VLAN 10 VLAN 30 Enable All Subinterfaces 28

29 Chapter 6 Inter-VLAN Routing Troubleshooting Inter-VLAN Routing 29

30 Chapter 6 Configuring Inter-VLAN Routing Switch Configuration Issues: VLAN 30 is working but VLAN 10 cannot communicate with the router or VLAN 30. Interface F0/4 is still in the default VLAN. switchport access vlan 10 30

31 Chapter 6 Configuring Inter-VLAN Routing Switch Configuration Issues: Each of the configured subinterfaces is unable to send or receive VLAN traffic. Interface F0/4 is still in the default VLAN. switchport mode trunk 31 F0/4

32 Chapter 6 Configuring Inter-VLAN Routing Router Configuration Issues: PC1 cannot communicate with the router interface and the router cannot route to VLAN 30. Switch port F0/9 is assigned to the default VLAN. Switch port F0/4 is for VLAN 10. Move the cable from F0/9 to F0/4. One of the most common mistakes in Inter-VLAN routing. Move the cable from F0/9 to F0/4. 32

33 Chapter 6 Configuring Inter-VLAN Routing Router Configuration Issues: PC1 cannot communicate with the router interface and the router cannot route to VLAN 30. 33

34 Chapter 6 Configuring Inter-VLAN Routing IP Addressing Issues: Incorrect IP address for subnet 172.16.10.0/24. Incorrect subnet mask for subnet 172.16.10.0/24. PC1 cannot communicate. 34


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