dup loop

/d[y]oop loop/ (also `dupe loop') [FidoNet] n. An incorrectly configured system or network gateway may propagate duplicate messages on one or more echoes, with different identification information that renders dup killers ineffective. If such a duplicate message eventually reaches a system through which it has already passed (with the original identification information), all systems passed on the way back to that system are said to be involved in a dup loop.