Interval Routing: Exploring Three Approaches

VLAN, Router on a Stick, and Layer 3 Switch

1. Per VLAN and Per Router Interface:

This approach involves configuring interval routing on a per-VLAN and per-router interface basis. It allows multiple VLANs to be supported on a single router interface, each with its own IP subnet.

Technical Implementation:

1. Create VLANs: Configure individual VLANs with their corresponding IP subnets using commands such as:

vlan database vlan 10 vlan 20 exit

2. Assign IPs: Assign IP addresses to each VLAN interface:

interface vlan 10 ip address 192.168.10.1 255.255.255.0 exit interface vlan 20 ip address 192.168.20.1 255.255.255.0 exit

Advantages:

• Isolation: Each VLAN maintains its own routing domain, enhancing security.
• Flexibility: Different IP subnets can be used for different VLANs, facilitating network management.

2. Router on a Stick:

This method involves using a single router interface for routing between multiple VLANs. It relies on subinterfaces to segment traffic from different VLANs.

Technical Implementation:

1. Create Subinterfaces: Divide a router interface into multiple subinterfaces, each associated with a specific VLAN:

interface gig0/0.10 encapsulation dot1Q 10 ip address 192.168.10.1 255.255.255.0 exit interface gig0/0.20 encapsulation dot1Q 20 ip address 192.168.20.1 255.255.255.0 exit

2. Enable Routing: Enable routing on the main interface:

interface gig0/0 no shutdown exit

Advantages:

• Simplified Configuration: Uses a single router interface, reducing complexity.
• Cost-Effective: Requires fewer physical interfaces, which can be cost-effective in terms of hardware.

3. Layer 3 Switch:

Layer 3 switches combine the features of switches and routers, offering hardware-based routing capabilities. They allow routing between VLANs at wire speed, making them suitable for high-speed networks.

Technical Implementation:

1. Enable Routing: Enable IP routing on the layer 3 switch:

enable configure terminal ip routing

2. Create VLAN Interfaces: Configure SVIs (Switched Virtual Interfaces) for each VLAN:

interface vlan 10 ip address 192.168.10.1 255.255.255.0 exit interface vlan 20 ip address 192.168.20.1 255.255.255.0 exit

Advantages:

• High Performance: Layer 3 switches offer fast routing due to hardware acceleration.
• Scalability: Suitable for networks with a large number of VLANs.

Comparison of Approaches:

Aspect	Per VLAN/Interface	Router on a Stick	Layer 3 Switch
Complexity	Moderate	Low	Low
Performance	Good	Moderate	High
Isolation	High	Low	High
Scalability	Moderate	Moderate	High
Hardware Requirements	Multiple Interfaces	Single Interface	Layer 3 Switch
Cost	Moderate	Low	Moderate

Comparison of Approaches of INterVLAN Routing

In conclusion, interval routing is a critical aspect of network design. The choice of approach depends on factors such as network size, performance requirements, and complexity considerations. Per VLAN/Interface offers isolation but may require more interfaces. Router on a Stick is cost-effective but has moderate performance. Layer 3 switches provide high performance and scalability at a moderate cost. Understanding these methods helps network administrators make informed decisions when designing and optimizing their networks.