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Are you ready to dive into Cisco trunk port configuration and understand how to connect VLANs across multiple switches seamlessly? In this comprehensive guide, we’ll walk through everything you need to know—from basic trunking concepts to real-world examples, commands, and best practices. Whether you’re preparing for your CCNA certification or working in a live production network, this guide will help you confidently configure and troubleshoot Cisco switch trunk ports. Table of Contents ✅ What is a Trunk Port in Cisco Switches? A trunk port is a switch port configured to carry traffic for multiple VLANs between switches or other network devices. Unlike access ports (which carry traffic for a single VLAN), trunk ports use 802.1Q tagging to identify the VLAN each frame belongs to. When configuring trunk ports on a Cisco switch, you enable inter-VLAN communication, which is critical for larger, segmented networks. Why Trunk Ports Are Important Trunk ports play a vital role in network scalability and segmentation. Here’s why: For example, if you have VLAN 10 (HR) and VLAN 20 (Sales) on Switch A and the same VLANs on Switch B, you can use a trunk port to pass both VLANs across a single link. How to Configure a Trunk Port on a Cisco Switch Let’s walk through configuring a trunk port on a Cisco switch using CLI commands. Here’s a simple topology: Switch-A —- Trunk Link —- Switch-B We’ll configure GigabitEthernet 0/1 on switch-A and GigabitEthernet 0/2 on Switch-B Step-by-Step Trunk Configuration SwitchA> enableSwitchA# configure terminalSwitchA(config)# interface gigabitEthernet 0/1SwitchA(config-if)# switchport mode trunkSwitchA(config-if)# switchport trunk allowed vlan 10,20SwitchA(config-if)# exitSwitchA(config)# exitSwitchA# write memory Repeat the same on SwitchB. This is a basic Cisco trunk port configuration. It uses the switchport mode trunk command to set the port to trunk mode, and the switchport trunk allowed vlan 10,20 command to allow only VLANs 10 and 20 across the trunk. Cisco Trunk Commands Explained Here’s a breakdown of some commonly used Cisco switch trunk commands: Command Description switchport mode trunk Puts the interface into trunking mode. switchport trunk allowed vlan 10,20 Allows specific VLANs on the trunk port. switchport trunk native vlan 99 Sets the native VLAN (untagged VLAN). show interfaces trunk Verifies trunk status and VLANs allowed. Example: Allow only VLANs 10 and 20 switchport trunk allowed vlan 10,20 This command sets the port to Cisco allow VLAN on trunk selectively, instead of allowing all. For more details, refer to Cisco’s official VLAN trunking documentation. Allowing VLANs on a Trunk Port To allow VLANs on a trunk port, use this format: switchport trunk allowed vlan <vlan-list> Example: Switch(config-if)# switchport trunk allowed vlan 10,20 This setup ensures that only VLANs 10, 20, and 99 can pass through the trunk. This is an example of Cisco VLAN trunk customization. ⚠️ Avoid using switchport trunk allowed vlan all unless you intend to allow every VLAN. 🔎 Troubleshooting Cisco VLAN Trunks If your VLANs aren’t communicating, check the following: 1. Interface Not in Trunk Mode Verify with: show interfaces switchport 2. VLAN Not Allowed Verify VLANs allowed on trunk: show interfaces trunk 3. VLAN Not Created Make sure the VLAN exists: show vlan brief 4. Mismatched Native VLANs Ensure both sides have the same native VLAN to avoid traffic issues. Best Practices for Cisco Trunk Configuration When working with Cisco switchport mode trunk, keep these best practices in mind: You can explore more Cisco switch trunk best practices at Cisco Networking Academy. Related Networking Articles from FaizanTech Core If you want to understand Port Security on Cisco switches alongside trunking, read our detailed blog post on Cisco Port Security in Switch – Complete Configuration Guide. Also, check out our beginner-friendly guide on Layer 2 vs Layer 3 Switch – Key Differences You Must Know in 2025 to understand how trunks impact broadcast traffic and where switching decisions are made. Bookmark www.faizantechcore.com for more CCNA, networking, and security blogs! Enhancing Your Cisco Trunk Port Configuration Skills When working in enterprise or campus networks, mastering Cisco trunk port configuration becomes a critical skill for any network engineer or IT professional. A well-designed trunk setup ensures seamless VLAN communication across multiple switches and maintains efficient traffic segmentation. Whether you’re building new infrastructure or expanding an existing one, understanding the principles behind Cisco trunk port configuration helps avoid broadcast storms, misconfigured VLANs, and downtime. With proper planning and implementation, your Cisco trunk port configuration will support a scalable and secure network architecture. Conclusion Mastering Cisco trunk port configuration is essential for any network engineer. It enables inter-VLAN communication, reduces cabling, and offers better scalability. Here’s a quick recap: By applying these concepts and commands, you’ll build a stronger, more reliable, and scalable network. For more networking tutorials, visit www.faizantechcore.com regularly!

STP in Networking: Step-by-Step Guide for Beginners In networking, loops can cause serious issues like broadcast storms, MAC table instability, and multiple frame transmissions. To prevent these problems, Cisco switches use the Spanning Tree Protocol (STP), a layer-2 protocol that ensures a loop-free topology in a network with redundant links. If you’re new to networking or Cisco devices, understanding STP is crucial for designing efficient and stable networks. In this guide, we’ll cover: By the end of this guide, you’ll have a solid understanding of STP and how to implement it in Cisco environments. What is Spanning Tree Protocol (STP)? Definition of STP Spanning Tree Protocol (STP) is a network protocol designed to prevent loops in Ethernet networks. It was developed by Radia Perlman in 1985 and later standardized as IEEE 802.1D. Why Do We Need STP? In a network with redundant paths, loops can occur, leading to: STP prevents these issues by logically blocking redundant paths while keeping them as backups in case the primary link fails. How Does STP Work? Key Concepts of STP STP Port States STP transitions ports through different states: This process ensures a loop-free topology while maintaining redundancy. Different Versions of STP Cisco switches support multiple STP versions, each with improvements over the original protocol. 1. Per-VLAN Spanning Tree (PVST+) 2. Rapid Spanning Tree Protocol (RSTP – IEEE 802.1w) 3. Multiple Spanning Tree Protocol (MSTP – IEEE 802.1s) Configuring STP on Cisco Switches Basic STP Configuration To enable STP on a Cisco switch: Switch(config)# spanning-tree mode pvst # Sets PVST+ as the STP mode Switch(config)# spanning-tree vlan 1 root primary # Makes this switch the root bridge for VLAN 1 Switch(config)# spanning-tree vlan 1 priority 4096 # Manually sets bridge priority Verifying STP Configuration Use these commands to check STP status: Switch# show spanning-tree # Displays STP information Switch# show spanning-tree vlan 1 # Shows STP details for VLAN 1 Switch# show spanning-tree interface gig0/1 # Checks STP status on a specific port Changing STP Port Costs To influence path selection, adjust port costs: Switch(config)# interface gig0/1 Switch(config-if)# spanning-tree cost 10 # Lower cost = preferred path Common STP Issues and Troubleshooting 1. Slow Convergence 2. Root Bridge Placement Issues 3. BPDU Filtering Problems 4. PortFast Misconfiguration Switch(config)# interface gig0/2 Switch(config-if)# spanning-tree portfast Best Practices for STP in Cisco Networks For more advanced networking guides, check out our Cisco Switching & Routing tutorials. Conclusion Spanning Tree Protocol is a fundamental concept in network switching that prevents loops while maintaining redundancy. By understanding STP, its versions, and best practices, you can design efficient and stable Cisco networks. Whether you’re preparing for CCNA or managing enterprise networks, mastering STP is essential. If you found this guide helpful, explore more networking topics on FaizanTechCore.com. Got questions? Drop them in the comments below! 🚀 External References This guide covers all the basics of STP in Cisco switches—now you’re ready to implement it in your network!

Layer 2 vs Layer 3 Switch: Key Differences You Must Know in 2025 Discover the key differences between Layer 2 vs Layer 3 switches in 2025. Learn how each works, when to use them, and which is right for your network infrastructure Introduction In networking, switches play an important role directing traffic through an intelligent way. However, not all switches are the same mostly two types of switches are used in networking—Layer 2 vs Layer 3 switches serve different purposes. Understanding their differences helps in choosing the right device for your network. Let’s dive in! This guide will explain:✔ What is a Layer 2 switch?✔ What is a Layer 3 switch?✔ Key differences between Layer 2 and Layer 3 switches✔ When to use each type✔ Layer 3 switch vs router comparison What is a Layer 2 Switch? In the OSI model, a Layer 2 switch functions at the Data Link Layer (Layer 2). Data is forwarded inside a local network segment (broadcast domain) using MAC addresses.What’s the Process of a Layer 2 Switch? Keeps track of MAC addresses to assign devices to the appropriate ports.  Eexplore more networking topics on FaizanTechCore.com. Key Features of a Layer 2 Switch ✅ MAC Address Learning – Dynamically builds a MAC table.✅ VLAN Support – Segments traffic but requires a router for inter-VLAN communication.✅ High-Speed Switching – Low latency since it doesn’t process IP routing.✅ Broadcast Domain Control – Reduces unnecessary traffic via VLANs. When to Use a Layer 2 Switch? What is a Layer 3 Switch? A Layer 3 switch operates at both Layer 2 (Data Link) and Layer 3 (Network) of the OSI model. It combines switching and routing capabilities, allowing it to forward traffic based on IP addresses. How Does a Layer 3 Switch Work? Key Features of a Layer 3 Switch ✅ Inter-VLAN Routing – Eliminates the need for an external router.✅ IP Routing – Forwards traffic based on IP addresses.✅ Combines Switching & Routing – Faster than traditional router + switch setups.✅ ACLs & QoS Support – Enhances security and traffic prioritization. When to Use a Layer 3 Switch? Layer 2 vs Layer 3 Switch: Key Differences Feature Layer 2 Switch Layer 3 Switch OSI Layer Data Link (Layer 2) Network (Layer 3) + Data Link (Layer 2) Forwarding Basis MAC addresses IP addresses + MAC addresses VLAN Routing No (requires a router) Yes (built-in inter-VLAN routing) Broadcast Control Uses VLANs to limit broadcasts Can route between VLANs Routing Protocols No support Supports RIP, OSPF, etc. Performance Faster (no routing overhead) Slightly slower due to routing Use Case Single subnet/VLAN networks Multi-VLAN, enterprise networks Layer 3 Switch vs Router: What’s the Difference? Feature Layer 3 Switch Router Primary Function High-speed LAN routing & switching WAN/Internet routing Routing Performance Faster for LAN traffic Slower but optimized for WAN Port Density More Ethernet ports Fewer ports, often with WAN interfaces NAT & Firewall Limited support Full support Use Case Enterprise LANs with multiple VLANs Connecting to ISPs, VPNs, WAN links When to Use Layer 2 vs Layer 3 Switch? Choose a Layer 2 Switch If: Choose a Layer 3 Switch If: Conclusion When comparing Layer 2 vs Layer 3 switches, it’s important to understand their roles in a network. Layer 2 switches are ideal for basic switching within a single VLAN. On the other hand, Layer 3 switches add routing capabilities, making them perfect for multi-VLAN enterprise networks. While routers are still needed for WAN/Internet connectivity, Layer 3 switches help optimize LAN routing. By understanding these differences in Layer 2 vs Layer 3 switches, you can confidently choose the right switch for your network needs. FAQs 1. Can a Layer 3 switch replace a router?No, Layer 3 switches are best for LAN routing, while routers handle WAN/Internet connections. 2. Do Layer 2 switches support VLANs?Yes, but they cannot route between VLANs—you need a Layer 3 switch or router. 3. Is a Layer 3 switch faster than a router?For LAN traffic, yes—Layer 3 switches are optimized for high-speed internal routing. 4. When should I upgrade from Layer 2 to Layer 3?When your network grows, and you need inter-VLAN routing without a bottleneck. External References

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