Chapter 6 Inter – VLAN Routing pot
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CCNA – Semester 3
Chapter 6 -
Inter – VLAN Routing
CCNA Exploration version 4.0
2
Objectives
• Explain 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.
3
Introduction
4
Introduction
Inter-VLAN Routing permits computers on separate VLANs
can communicate with each other
5
Traditional Inter-VLAN Routing
• In a traditional network that uses multiple VLANs to
segment the network traffic into logical broadcast domains,
routing is performed by connecting different physical router
interfaces to different physical switch ports.
6
"Router-on-a-stick" Inter-VLAN Routing
• "Router-on-a-stick" is a type of router configuration in which
a single physical interface routes traffic between multiple
VLANs on a network.
7
Switched-based Inter-VLAN Routing
• 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.
8
Interface and Subinterface
9
Interface
• 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.
10
Interface Configuration
11
Subinterface
• To overcome the hardware limitations of inter-VLAN routing
based on router physical interfaces, virtual subinterfaces and
trunk links are used.
• Each subinterface is configured with its own IP address,
subnet mask, and unique VLAN assignment, allowing a
single physical interface to simultaneously be part of multiple
logical networks.
• Functionally, the router-on-a-stick model for inter-VLAN
routing is the same as using the traditional routing model,
but instead of using the physical interfaces to perform the
routing, subinterfaces of a single interface are used.
12
Subinterface (cont)
13
Subinterface Configuration
14
Comparison
Features Physical Interface Subinterface
Port Limits
One physical interface
per VLAN
One physical interface for
many VLANs
Performance No bandwidth contention Bandwidth contention
Access Ports and
Trunk Ports
Connected to access
mode switch port
Connected to trunk mode
switch port
Cost More expensive Less expensive
Complexity
More complex
connection configuration
Less complex connection
configuration
15
Configure Inter-VLAN Routing
16
Configure Traditional Inter-VLAN Routing
Switch Configuration
17
Configure Traditional Inter-VLAN Routing
Router Configuration
18
Configure Traditional Inter-VLAN Routing
19
Configure Router-on-a-Stick Inter-VLAN Routing
Switch Configuration
20
Configure Router-on-a-Stick Inter-VLAN Routing
Router Configuration
21
Configure Router-on-a-Stick Inter-VLAN Routing
22
Some ISSUES with
Inter-VLAN Routing
23
Switch Configuration Issues
• Switch ports are not configured on the correct VLAN
• No redundant connection or path between the devices
24
Router Configuration Issues
• Connect the physical router interface to the wrong switch
port, placing it on the incorrect VLAN and preventing it from
reaching the other VLANs.
25
Router Configuration Issues
Router R1 has been configured to use the wrong VLAN on
subinterface F0/0.10, preventing devices configured on
VLAN10 from communicating with subinterface F0/0.10
