'''Simple Loop Prevention Protocol''' ('''SLPP''') in [[computer networking]] is a [[Data linkLink layer|layer 2Layer]] protocol inventeddeveloped by [[Nortel]] (previously acquired by [[Avaya]], now acquireda part of by [[Extreme Networks]]) to protect against Layer 2 network loops. SLPP uses a small hello packet to detect network loops. The SLPP protocol checks packets from the originating switch and the peer switch in a [[SMLT]] configuration. Sending hello packets on a per VLAN basis allows SLPP to detect VLAN based network loops for un-tagged as well as tagged IEEE 802.1Q VLAN link configurations. OnceIf a loop is detected, the associated port is shut down.
