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.

Table of Contents

1 Project Plan and Configuration Overview
2 Step Configuration Cisco Packet Tracer
3 🧠 Overview: Cisco Catalyst WS-C4500X-F-32SFP+
4 🛒 Buying Tips for Renewed Cisco Gear
5 🔍 Comparison Table: Cisco Catalyst Switches
6 🏆 Highlights of WS-C4500X-F-32SFP+
7 🧠 When to Choose Other Models
8 🧠 Layer 3 Features of WS-C4500X-F-32SFP+
9 ⚠️ Licensing Note

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.

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

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

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.

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

Cisco Catalyst WS-C4500X-F-32SFP+ 4500-X 32 Port 10GE IP Base Switch (Renewed)

9.4

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Feature	WS-C4500X-F-32SFP+	Catalyst 9300 Series	Catalyst 3850 Series	Catalyst 9500 Series
Ports	32 × 10GE SFP+	Up to 48 × 1GE (modular uplinks)	Up to 48 × 1GE + 4 × 10GE uplinks	12–40 × 10GE/40GE
Layer Support	Layer 2 & basic Layer 3 (IP Base)	Full Layer 3 (IP Services)	Layer 3 with IP Base/IP Services	Advanced Layer 3 (Enterprise Services)
Stacking	Virtual Switching System (VSS)	StackWise-480	StackWise-480	No stacking, but high redundancy
Switching Capacity	800 Gbps	Up to 480 Gbps	Up to 640 Gbps	Up to 6.4 Tbps
Use Case	Aggregation/Data Center	Access Layer (Campus/Branch)	Access/Distribution	Core/Distribution
PoE Support	❌ No	✅ Yes (PoE/PoE+/UPOE)	✅ Yes	❌ No
Airflow	Front-to-back	Side-to-side	Side-to-side	Front-to-back
Software	Cisco IOS XE	Cisco IOS XE	Cisco IOS XE	Cisco IOS XE
Virtualization	EVN, VSS	SD-Access, DNA Center	EVN, VSS	SD-Access, DNA Center

🏆 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