How to Prevent VLAN-Hopping in MSP Networks. VLAN hopping is a network attack that bypasses segmentation through double-tagging or switch spoofing. Both techniques only need small configuration gaps to infiltrate a network. Thankfully, there are a number of ways to protect yourself against VLAN hopping. In this video, we’ll go through those different methods. Before we begin, be sure to subscribe to NinjaOne’s IT video hub and our YouTube channel for more tech content like this. Lock Down Access Ports. Locking down access ports is one of the most effective first lines of defense against VLAN hopping. This prevents unauthorized trunking by ensuring that user endpoints are confined to designated VLANs. This method involves the following steps: Setting all non-uplink ports to switchport mode access Disabling Dynamic Trunking Protocol to prevent automatic trunk formation, Assigning the correct VLANs explicitly and removing any unused VLAN memberships to reduce exposure Using LLDP or CDP to detect IP phones and limit voice VLAN activation to authorized devices only. Make Trunks Explicit and Safe. Configuring trunk ports prevents them from being used in VLAN hopping and traffic injection. To do this, you need to: Manually configure trunk ports and restrict VLANs to only those necessary for inter-switch communication. Set up a dedicated, unused native VLAN and, where supported, configure native VLAN tagging to help prevent untagged traffic exploitation. Reserve VLAN 1 for internal use only or prune it globally to prevent retention of user or management traffic. Enforce Admission and Segmentation Policy. Not all endpoints have equal access. This is where identity-based admission and trust-level network segmentation come in. This includes: Enabling 802.1X authentication on edge ports and dynamically assigning VLANs based on user or device identity. Applying inter-VLAN ACLs at Layer 3 Isolating guest and IoT networks with minimal routing paths Other Methods. Other ways you can protect yourself against VLAN hopping include: Enabling Layer 2 Protections. Enabling built-in switch protections such as DHCP Snooping, Dynamic ARP Inspection (DAI), BPDU Guard, Root Guard, and Storm Control helps protect your network from Layer 2 attacks such as spoofing and flooding. By activating these protections, you make lateral movement from such attacks more difficult. Monitor, Audit, and Prove. Vigilance is always a part of any cybersecurity strategy. This involves setting real-time alerts for critical changes, generating and reviewing regular reports, and recording incident data. VLAN hopping may sound complex, but the defenses are straightforward. Lock down your access ports, secure your trunk links, and monitor your network regularly, that's how you keep attackers out. For more information, check out our official blog post on How to Prevent VLAN-Hopping in MSP Networks linked in the description below.