Chap 6

1
Chap 6 Implement Inter-VLAN Routing Learning
Objectives

• Explain to the satisfaction of a qualified
  instructor how network traffic is routed between
  VLANs in a converged network.
• Configure inter-VLAN routing on a router to
  enable communications between end-user devices on
  separate VLANs
• Troubleshoot common inter-VLAN connectivity
  issues.

2
Inter-VLAN Routing
Link to VLAN 10
Link to VLAN 20
Link to VLAN 30

• Inter-VLAN routing can be performed by connecting
  different physical router interfaces to different
  physical switch ports.
• The switch ports connect to the router in access
  mode, and different static VLANs are assigned to
  each port interface.
• Each switch interface would be assigned to a
  different static VLAN. Each router interface can
  then accept traffic from the VLAN associated with
  the switch interface that it is connected to, and
  traffic can be routed to the other VLANs
  connected to the other interfaces.

S3
S1
Fa0/1
Fa0/1
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
Fa0/2
Fa0/3
S2
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)
3
Router-on-a -Stick
"Router-on-a-stick" is a type of router
configuration in which a single physical
interface routes traffic between multiple VLANs
on a network.
R1 - Fa0/0 Sub-interfaces Fa0/0.10 172.17.10.1
Default Gateway to VLAN 10 Fa0/0.20
172.17.20.1 Default Gateway to VLAN 20
Fa0/0.30 172.17.30.1 Default Gateway to VLAN
30
Fa0/0
S3
S1
Fa0/1
Fa0/1
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
Fa0/2
Fa0/3
S2
Sub-interfaces are multiple virtual interfaces,
associated with one physical interface. These
sub-interfaces are configured with an IP address
and VLAN assignment to operate on a specific VLAN.
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)

• Sub-interfaces are configured for different
  subnets corresponding to their VLAN assignment to
  allow logical routing before data frames are VLAN
  tagged and sent back out the physical interface.

4
Layer-3 Switch
S1 VLAN Interfaces 172.17.10.1 Default Gateway
to VLAN 10 172.17.20.1 Default Gateway to VLAN
20 172.17.30.1 Default Gateway to VLAN 30
S3
S1
Fa0/1
Fa0/1
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/4
Fa0/3
Fa0/2
Fa0/3
S2

• Some switches can perform Layer 3 functions,
  replacing the need for dedicated routers to
  perform basic routing on a network.
• Multilayer switches are capable of performing
  inter-VLAN routing.

Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)

• To enable a multilayer switch to perform routing
  functions, VLAN interfaces on the switch need to
  be configured with the appropriate IP addresses
  that match the subnet that the VLAN is associated
  with on the network. The multilayer switch also
  must have IP routing enabled.

5
Connecting VLANs

• Switch Virtual Interface (SVI) is a logical
  interface configured for a specific VLAN, and is
  used by layer 3 switches to route between VLANs
  or to provide IP host connectivity to a switch.

• A Layer 3 switch has the ability to route
  transmissions between VLANs.
• The process is the same as when using a separate
  router, except that the SVIs act as the router
  interfaces for routing the data between VLANs.

SVI VLAN99
SVI VLAN30
Management VLAN 99 172.17.99.10/24
SVI VLAN20
Layer 3 Switch
Fa0/1
Fa0/3
Student VLAN 20 172.17.20.22/24
Student VLAN 20 172.17.20.25/24
Fa0/18
Fa0/18
Fa0/1
Fa0/3
Guest VLAN 30 172.17.30.23/24
Guest VLAN 30 172.17.30.26/24
Fa0/6
Fa0/6
6
Physical Interface Configuration
Fa0/0 172.17.10.1/24
Fa0/1 172.17.30.1/24
S3
S1
Fa0/6
Fa0/5
Fa0/1
Fa0/1
Configure Router Interfaces
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
Fa0/2
Fa0/3
S2
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)
7
Sub-Interface Configuration
Fa0/0.10 172.17.10.1/24
Fa0/0.30 172.17.30.1/24
S3
S1
Fa0/1
Fa0/1
Fa0/5
Configure Router Interfaces
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
Fa0/2
Fa0/3
S2
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)

• To avoid confusion, name the sub-interface after
  the VLAN to which it is attached e.g. Fa0/0.10
  is connected to VLAN 10

8
Sub-Interface Configuration
Fa0/0.10 172.17.10.1/24
Fa0/0.30 172.17.30.1/24
S3
S1
Fa0/1
Fa0/1
Fa0/5
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
S1 Fa0/5 must be configured as a trunk to allow
it to carry tagged data from multiple VLANs
Fa0/2
Fa0/3
S2
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24 (VLAN 10)
PC2 172.17.20.22/24 (VLAN 20)
PC3 172.17.30.23/24 (VLAN 30)
9
Interface and Sub-Interface Comparison
10
Chap 6 Implement Inter-VLAN Routing Learning
Objectives

• Explain to the satisfaction of a qualified
  instructor how network traffic is routed between
  VLANs in a converged network.
• Configure inter-VLAN routing on a router to
  enable communications between end-user devices on
  separate VLANs
• Troubleshoot common inter-VLAN connectivity
  issues.

11
Any Questions?
12
Lab Topology
Chap 6.2.2.4 Basic Inter-VLAN Routing
Fa0/0
Fa0/1
Fa0/8
Fa0/5
Fa0/11
Fa0/6
PC1 172.17.10.10/24
PC3 172.17.30.10/24
13
Lab Topology
Chap 6.2.2.5 Router-On-A-Stick Inter-VLAN
Routing
Fa0/1
Fa0/5
Fa0/11
Fa0/6
PC1 172.17.10.10/24
PC3 172.17.30.10/24
14
Lab Topology
Chap 6.4.1 Basic VLAN Routing
Fa0/1 172.17.50.1
Server 172.17.50.254/24
Fa0/0
S3
S1
Fa0/1
Fa0/1
Fa0/2
Fa0/2
Fa0/3
Fa0/4
Fa0/3
Fa0/4
Fa0/2
Fa0/3
S2
Fa0/1
Fa0/4
Fa0/11
Fa0/6
Fa0/18
PC1 172.17.10.21/24
PC2 172.17.20.22/24
PC3 172.17.30.23/24