I'm reasonable certain a customer of ours who is using one of our netblocks is using a different reverse path to reach us. How might I figure out who is allowing them to source traffic from IPs that belong to us? you are implying that they are not allowed to multi-home using the ip space you have assigned to them. good way to lose a customer. Does it count as multihoming when we are the only ones announcing the space?
almost an interesting question. but i think it is playing with words. if i understand your original statement, they are clearly attached to at least two providers. perhaps it is fear of what they, possibly mistakenly, perceive to be your policy regarding announcement of space that keeps them from announcing normally to both, or more, links? randy