VLAN
Virtual Local Area Network
A logical network segment that isolates traffic on shared switches.
A VLAN logically segments a shared physical switch into separate broadcast domains so traffic in one segment cannot reach another without a router or layer 3 device. This isolation limits an attacker's lateral movement and contains broadcast traffic. Membership is commonly tagged using 802.1Q. A frequent exam pitfall is VLAN hopping, where double tagging or switch spoofing lets traffic cross segments, which is why unused ports and native VLAN settings should be hardened.
Looking VLAN up is step one. Getting tested on it is step two.
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