Module 3: VLANs
1. Overview of VLANs:
○ Definition and Benefits of VLANs:
■ VLANs (Virtual Local Area Networks) are used to segment
networks into smaller, isolated networks to reduce
broadcast traffic, improve security, and enhance network
performance.
■ Benefits:
■ Smaller broadcast domains, improved security,
enhanced IT efficiency, reduced cost, better
■ performance, and simpler management.
○ Types of VLANs:
■ Default VLAN: VLAN 1, the default VLAN for all ports.
■ Native VLAN: A VLAN not tagged on a trunk link, typically
used for backward compatibility.
■ Management VLAN: A VLAN used to manage the network
devices.
2. VLANs in a Multi-Switched Environment:
○ VLAN Trunks:
■ A trunk is a point-to-point link between network devices
carrying multiple VLANs. Cisco trunking supports the
802.1Q protocol, which allows VLANs to span across the
entire network.
○ Networks without VLANs:
■ Without VLANs, all devices connected to the switches
receive all types of network traffic, including unicast,
multicast, and broadcast traffic.
○ Networks with VLANs:
, ■ With VLANs, traffic is limited to devices within the same
VLAN. Communication between different VLANs requires a
Layer 3 device (like a router).
○ VLAN Identification with a Tag:
■ The IEEE 802.1Q header, which is 4 bytes, is used for
VLAN tagging. It includes fields like Type (Tag Protocol ID),
User Priority, Canonical Format Identifier (CFI), and VLAN
ID (VID).
3. VLAN Configuration:
○ VLAN Creation Commands:
■ Commands to create a VLAN in Cisco IOS, including
defining a VLAN ID and assigning a name.
○ VLAN Port Assignment Commands:
■ Steps to assign VLANs to specific switch ports, including
setting ports to access mode.
○ Verifying VLAN Configuration:
show vlanto display and verify VLAN
■ Commands like
information.
○ Changing VLAN Port Membership:
■ Instructions on how to change VLAN membership by
modifying port settings.
○ Deleting VLANs:
■ Procedures to delete individual or all VLANs and reset
switches to default settings.
4. VLAN Trunks:
○ Trunk Configuration Commands:
■ Instructions for setting up trunk links, including setting
trunk mode and specifying VLANs allowed on the trunk.
○ Verifying Trunk Configuration:
, show
■ Steps to confirm trunk settings using commands like
interfaces trunk
.
○ Resetting Trunk to Default:
■ Steps to reset trunk settings to default, such as restoring
VLAN 1 as the native VLAN.
Module 4: Inter-VLAN Routing
1. Inter-VLAN Routing Operation:
○ What is Inter-VLAN Routing?:
■ Process of forwarding traffic between VLANs using routers
or Layer 3 switches. Inter-VLAN routing allows
communication between hosts on different VLANs.
■ Inter-VLAN Routing Options:
■ Legacy Inter-VLAN Routing: Uses a router with
multiple Ethernet interfaces; not scalable.
■ Router-on-a-Stick: Uses a single router interface
configured as a trunk with multiple subinterfaces;
suitable for small to medium-sized networks.
■ Layer 3 Switch with SVIs (Switched Virtual
Interfaces): Provides the most scalable solution for
medium to large networks.
2. Legacy Inter-VLAN Routing:
○ Description:
■ Uses separate physical interfaces on a router for each
VLAN. This method is no longer commonly used due to
scalability issues.
3. Router-on-a-Stick Inter-VLAN Routing:
1. Overview of VLANs:
○ Definition and Benefits of VLANs:
■ VLANs (Virtual Local Area Networks) are used to segment
networks into smaller, isolated networks to reduce
broadcast traffic, improve security, and enhance network
performance.
■ Benefits:
■ Smaller broadcast domains, improved security,
enhanced IT efficiency, reduced cost, better
■ performance, and simpler management.
○ Types of VLANs:
■ Default VLAN: VLAN 1, the default VLAN for all ports.
■ Native VLAN: A VLAN not tagged on a trunk link, typically
used for backward compatibility.
■ Management VLAN: A VLAN used to manage the network
devices.
2. VLANs in a Multi-Switched Environment:
○ VLAN Trunks:
■ A trunk is a point-to-point link between network devices
carrying multiple VLANs. Cisco trunking supports the
802.1Q protocol, which allows VLANs to span across the
entire network.
○ Networks without VLANs:
■ Without VLANs, all devices connected to the switches
receive all types of network traffic, including unicast,
multicast, and broadcast traffic.
○ Networks with VLANs:
, ■ With VLANs, traffic is limited to devices within the same
VLAN. Communication between different VLANs requires a
Layer 3 device (like a router).
○ VLAN Identification with a Tag:
■ The IEEE 802.1Q header, which is 4 bytes, is used for
VLAN tagging. It includes fields like Type (Tag Protocol ID),
User Priority, Canonical Format Identifier (CFI), and VLAN
ID (VID).
3. VLAN Configuration:
○ VLAN Creation Commands:
■ Commands to create a VLAN in Cisco IOS, including
defining a VLAN ID and assigning a name.
○ VLAN Port Assignment Commands:
■ Steps to assign VLANs to specific switch ports, including
setting ports to access mode.
○ Verifying VLAN Configuration:
show vlanto display and verify VLAN
■ Commands like
information.
○ Changing VLAN Port Membership:
■ Instructions on how to change VLAN membership by
modifying port settings.
○ Deleting VLANs:
■ Procedures to delete individual or all VLANs and reset
switches to default settings.
4. VLAN Trunks:
○ Trunk Configuration Commands:
■ Instructions for setting up trunk links, including setting
trunk mode and specifying VLANs allowed on the trunk.
○ Verifying Trunk Configuration:
, show
■ Steps to confirm trunk settings using commands like
interfaces trunk
.
○ Resetting Trunk to Default:
■ Steps to reset trunk settings to default, such as restoring
VLAN 1 as the native VLAN.
Module 4: Inter-VLAN Routing
1. Inter-VLAN Routing Operation:
○ What is Inter-VLAN Routing?:
■ Process of forwarding traffic between VLANs using routers
or Layer 3 switches. Inter-VLAN routing allows
communication between hosts on different VLANs.
■ Inter-VLAN Routing Options:
■ Legacy Inter-VLAN Routing: Uses a router with
multiple Ethernet interfaces; not scalable.
■ Router-on-a-Stick: Uses a single router interface
configured as a trunk with multiple subinterfaces;
suitable for small to medium-sized networks.
■ Layer 3 Switch with SVIs (Switched Virtual
Interfaces): Provides the most scalable solution for
medium to large networks.
2. Legacy Inter-VLAN Routing:
○ Description:
■ Uses separate physical interfaces on a router for each
VLAN. This method is no longer commonly used due to
scalability issues.
3. Router-on-a-Stick Inter-VLAN Routing:
