This guide will let you know where to get the System Reroute in Warframe.
System Reroute can drop as a B rotation reward from Archwing Rush missions. You can also run the archwing interception mission, and the grineer enemies that spawn in the interception mission have a chance to drop the mod.
To get the B rotation rewards and have a chance at getting the Mod, You need only to destroy 2 of the 3 transports and let the 3rd transport leave; it may take you more or fewer runs until you get the mod.
