IT-341 Module-10 Chapter-4 Inter-VLAN Routing

What is Inter-VLAN Routing?

The process of forwarding network traffic from one VLAN to another.

Why is Inter-VLAN Routing necessary?

Because devices in different VLANs cannot communicate directly without routing.

What are the 3 methods of Inter-VLAN Routing?

Legacy routing, Router-on-a-Stick, and Layer 3 switch using SVIs.

What is Legacy Inter-VLAN Routing?

Using multiple physical router interfaces connected to different VLANs.

What is the main disadvantage of Legacy Inter-VLAN Routing?

It doesn't scale well due to the limited number of physical interfaces.

What is Router-on-a-Stick?

A single physical router interface with multiple subinterfaces handling VLAN routing.

What is a subinterface?

A virtual interface created on a physical router interface for VLAN routing.

How is a subinterface named?

interface-id.subinterface-id (e.g., Gig0/0.10)

What command creates a subinterface?

interface [interface-id].[subinterface-number]

What command configures VLAN tagging on a subinterface?

encapsulation dot1q [VLAN-ID]

What command assigns an IP address to a subinterface?

ip address [ip-address] [subnet-mask]

What is a best practice when assigning subinterface numbers?

Match the subinterface number with the VLAN ID.

What is a switched virtual interface (SVI)?

A virtual interface on a Layer 3 switch for Inter-VLAN routing.

What command creates an SVI?

interface vlan [VLAN-ID]

What must be enabled for a Layer 3 switch to perform routing?

ip routing

What is a routed port?

A Layer 3 switch port configured as a Layer 3 interface (no switchport).

What are advantages of using Layer 3 switches for routing?

Faster routing, lower latency, scalable, no external links needed for routing.

What is the only disadvantage of Layer 3 switches?

Higher cost compared to routers.

What command enables routing globally on a Layer 3 switch?

ip routing

Can an SVI serve as the default gateway?

Yes, for all hosts within the associated VLAN.

What command verifies SVI status?

show ip interface brief

How is VLAN traffic carried between switches?

Using trunk links.

What is necessary between switches for VLANs to communicate?

Trunk ports configured with the correct VLANs.

What must match on both ends of a trunk link?

The native VLAN and allowed VLANs.

What happens if a VLAN is missing from the trunk?

Inter-VLAN communication fails for that VLAN.

What command verifies trunking status?

show interfaces trunk

What is a common reason for inter-VLAN routing to fail?

Missing VLANs, misconfigured trunks, or incorrect IP addressing.

What is the main scalability limit of Router-on-a-Stick?

Does not scale well beyond 50 VLANs.

What are typical steps to configure inter-VLAN routing on a router?

Create subinterfaces, assign IP addresses, enable trunking, and configure switches.

What command shows the VLAN configuration of an interface?

show interfaces [interface] switchport

What command shows the IP routing table?

show ip route

How can you check if the physical interface is up?

Use show ip interface brief and verify the status.

What happens if the physical interface is shutdown?

All subinterfaces will also be down.

What is the purpose of the no shutdown command on subinterfaces?

It is not needed; only the physical interface needs to be enabled.

What can cause a switch access port issue?

The access port is assigned to the wrong VLAN.

What can cause a switch trunk port issue?

The trunk is not configured or is missing allowed VLANs.

How to verify allowed VLANs on a trunk?

show interfaces trunk

What command shows VLAN membership for a port?

show vlan brief

What is the role of Layer 3 switches in large networks?

Provide fast, scalable inter-VLAN routing without external routers.

What happens if a VLAN is accidentally deleted?

All associated ports become inactive until the VLAN is recreated.

What tool helps verify host IP configuration?

ipconfig on Windows hosts.