Paul Wall wrote:
Isn't that what a routing loop is, when it loops back out to the transit/interface from which it entered?
Of course. I think the sensitivity comes in to whether the diagnosis "routing loop" is one of the cause or effect. I.E. "this routing loop appears to show a network problem" vs "this routing loop is THE problem" Loops could happen due to human error in creating duplicate static routes, which would often be the ISP's responsibility to fix. They can also happen when the end-user takes their network down for maintenance, which is something the ISP can't usually fix (short of providing a naildown to prevent the loop from appearing, which doesn't really "fix" anything). I've been the recipient of angry emails accusing us of incompetence in cases where the customer had taken their network down intentionally. So we started putting in naildowns anywhere that might be likely to happen.