How to Configure Sub-Interfaces on Cisco Router

Configuring sub-interfaces on a Cisco router in Packet Tracer facilitates communication between VLANs. It provides segmented networks within a single physical connection. In this guide, we’ll set up a Cisco router (Router0) with sub-interfaces. This will allow it to route traffic between VLANs. We will also assign static IP addresses to client PCs.

Project Plan and Configuration Overview

This setup is common in networks that use VLANs to separate different departments, user groups, or services within an organization. The network will include three VLANs: VLAN Default (VLAN-1), VLAN-2, and VLAN-3. The clients will use static IP addresses to connect to these VLANs.

1. Router (Router0): Configured with sub-interfaces for each VLAN.

• Router Interface Gi0/0: Trunk link connected to Switch0’s Gi0/1.

1. Switch (Switch0): Configured with VLANs and ports assigned to specific VLANs.

• Switch Port Gi0/1: Trunk link connected to Router0’s Gi0/0.
• Switch Port Fa0/1: Assigned to VLAN-1 (Default).
• Switch Port Fa0/2: Assigned to VLAN-2.
• Switch Port Fa0/3: Assigned to VLAN-3.

1. Clients: PCs with static IP addresses.

• PC0: VLAN-1 with IP 172.16.1.x/16
• PC1: VLAN-2 with IP 192.168.2.x/24
• PC2: VLAN-3 with IP 192.168.3.x/24

Step Configuration Cisco Packet Tracer

Right now, I am starting to configure or create all VLan on the Switch0. I am also setting up port access and port trunk on Switch0.

1. Set Up the Switch (Switch0)

• Create VLANs on Switch0:
• Access Switch0 and go to the CLI.
• Enter global configuration mode:
  enable configure terminal
• Create the VLANs:
  vlan 1 vlan 2 vlan 3
• Exit VLAN configuration mode.
• Assign Ports to VLANs:
• Configure Fa0/1 for VLAN-1 (Default):
  interface fa0/1
• switchport mode access
• switchport access vlan 1
• exit
• Configure Fa0/2 for VLAN-2:
  interface fa0/2
• switchport mode access
• switchport access vlan 2
• exit
• Configure Fa0/3 for VLAN-3:
• interface fa0/3
• switchport mode access
• switchport access vlan 3
• exit
• Configure Trunk Port on Gi0/1:
• Set Gi0/1 as a trunk port to allow VLAN traffic to the router:
  interface gi0/1
• switchport mode trunk
• exit

2. Configure Sub-Interfaces (Router0)

Now we configure on Cisco Router of Packet Tracer with Sub-Interfaces. Note that sub internet we need to configure the router only.

• Access Router0 and go to CLI mode:

  enable
  configure terminal

• Configure Sub-Interfaces for Each VLAN:
• Sub-Interface for VLAN-1 (Default):
  interface gigabitEthernet 0/0.1
• encapsulation dot1Q 1
• ip address 172.16.1.1 255.255.0.0 exit
• Sub-Interface for VLAN-2:
  interface gigabitEthernet 0/0.2
• encapsulation dot1Q 2
• ip address 192.168.2.1 255.255.255.0
• exit
• Sub-Interface for VLAN-3:
• interface gigabitEthernet 0/0.3
• encapsulation dot1Q 3
• ip address 192.168.3.1 255.255.255.0
• exit
• Verify Interface Configuration:
• Exit configuration mode and check interface settings:
  show ip interface brief

3. Configure Static IP Addresses on PCs

• PC0 (VLAN-1):
• Open PC0, go to Desktop > IP Configuration, and set:
  • IP Address: 172.16.1.2
  • Subnet Mask: 255.255.0.0
  • Default Gateway: 172.16.1.1
• PC1 (VLAN-2):
• Open PC1, go to Desktop > IP Configuration, and set:
  • IP Address: 192.168.2.2
  • Subnet Mask: 255.255.255.0
  • Default Gateway: 192.168.2.1
• PC2 (VLAN-3):
• Open PC2, go to Desktop > IP Configuration, and set:
  • IP Address: 192.168.3.2
  • Subnet Mask: 255.255.255.0
  • Default Gateway: 192.168.3.1

4. Test Connectivity Between VLANs

• Ping Between PCs:
• Open Command Prompt on each PC and ping the router’s sub-interface corresponding to their VLAN:
  • From PC0, ping 172.16.1.1
  • From PC1, ping 192.168.2.1
  • From PC2, ping 192.168.3.1
• To test inter-VLAN connectivity, try pinging PCs across VLANs:
  • From PC0 to PC1’s IP (192.168.2.2)
  • From PC1 to PC2’s IP (192.168.3.2)
  • From PC2 to PC0’s IP (172.16.1.2)
• Successful pings confirm that the router is routing traffic between VLANs.

We configured sub-interfaces on the router and assigned VLANs on the switch. This setup enabled inter-VLAN communication for PCs with static IP addresses in separate VLANs. This setup shows how VLAN segmentation can work with a single router interface. It is a fundamental skill in network design. Students who want to explore networking further should check out more tutorials. You can find tutorials on VLANs, subnetting, and routing concepts on How To Got (Cisco)!

🧠 Overview: Cisco Catalyst WS-C4500X-F-32SFP+

This is a high-performance, enterprise-grade switch designed for data centers and large-scale network environments. The “Renewed” label means it’s refurbished—tested and certified to work like new.

🔧 Key Features

• Ports: 32 × 10 Gigabit Ethernet SFP+ ports
• Form Factor: Fixed configuration, rack-mountable
• Software: IP Base feature set (supports Layer 2 and basic Layer 3 routing)
• Throughput: Up to 800 Gbps switching capacity
• Redundancy: Dual redundant power supplies (depending on configuration)
• Cooling: Front-to-back airflow (ideal for data center deployments)

✅ Pros

• High Port Density: Great for aggregating multiple 10GE links
• Enterprise Reliability: Cisco’s Catalyst line is known for stability and long-term support
• Scalability: Supports stacking and virtual switching for simplified management
• Energy Efficient: Designed for reduced power consumption in high-demand environments

⚠️ Considerations

• Renewed Status: Make sure it includes warranty or return options
• No PoE: Doesn’t support Power over Ethernet—only data transmission
• Licensing: Advanced features may require additional licenses
• Noise Level: Can be loud—best suited for server rooms, not office spaces

🛒 Buying Tips for Renewed Cisco Gear

• Check seller ratings and reviews
• Confirm warranty details (Amazon Renewed usually offers 90-day guarantee)
• Ask if it includes rack mounts, power cords, and transceivers (often sold separately)

🔍 Comparison Table: Cisco Catalyst Switches

🏆 Highlights of WS-C4500X-F-32SFP+

• Best for: High-speed aggregation in space-constrained environments
• Strengths: Dense 10GE ports, VSS support, robust throughput
• Limitations: No PoE, limited Layer 3 features unless upgraded

🧠 When to Choose Other Models

• Catalyst 9300: Ideal for campus access with full PoE and SD-Access support
• Catalyst 3850: Good balance for access/distribution with stacking and PoE
• Catalyst 9500: Built for core networks with ultra-high throughput and advanced routing

If you’re building a data center or need a powerful aggregation switch, the 4500X is a solid choice. But if you’re outfitting a campus or branch office, the 9300 or 3850 might be more versatile.

Absolutely! The Cisco Catalyst WS-C4500X-F-32SFP+ switch offers solid Layer 3 capabilities, especially for enterprise aggregation and distribution roles. Here’s a breakdown of what it can do at Layer 3:

🧠 Layer 3 Features of WS-C4500X-F-32SFP+

✅ IP Routing (IPv4 & IPv6)

• Supports static routing, RIP, OSPF, EIGRP, and BGP (with appropriate licensing)
• IPv6 support is built into hardware, allowing high-speed forwarding for modern dual-stack networks
• Dynamic hardware forwarding tables make it easier to migrate from IPv4 to IPv6

🔄 Multicast Routing

• Supports PIM-SM, PIM-DM, and IGMP snooping
• Useful for video streaming, conferencing, and other multicast-heavy applications

🧭 Virtual Routing and Forwarding (VRF)

• Includes Multi-VRF support for network segmentation
• Enables multiple virtual routing tables on the same physical switch—great for multi-tenant environments or isolating departments

🔗 Cisco Easy Virtual Network (EVN)

• Simplifies VRF deployment with easier configuration and management
• Ideal for organizations that want to virtualize their Layer 3 networks without complex setups

🧬 Virtual Switching System (VSS)

• Allows two physical switches to operate as one logical switch
• Provides high availability, simplified management, and nonstop forwarding during failover

🔐 Security & Control

• Cisco TrustSec for role-based access control
• Control Plane Policing (CoPP) to protect against denial-of-service (DoS) attacks
• Access Control Lists (ACLs) for traffic filtering and policy enforcement

📊 Application Visibility

• Flexible NetFlow for traffic monitoring and analytics
• SPAN/RSPAN for packet capture and remote analysis

🔄 High Availability Features

• Nonstop Forwarding (NSF) and Stateful Switchover (SSO) when used in VSS mode
• In-Service Software Upgrade (ISSU) support for minimal downtime during updates

⚠️ Licensing Note

The switch comes with the IP Base feature set by default, which includes basic Layer 3 routing. For advanced routing protocols (like BGP or full OSPF), you may need to upgrade to the Enterprise Services license.