BGP Upstream Checker
See which transit providers actually carry a prefix
A network can buy transit from several providers and still have almost all of its inbound traffic arrive over just one of them, because every remote router picks its own best path. This tool reads the live routing table from RIPE's RIS collectors and shows which upstream each vantage point actually uses to reach a prefix — the difference between the transit you pay for and the transit you get.
Frequently asked questions
What counts as an "upstream" here?
For every path a route collector sees, we take the network sitting immediately in front of the origin. That is the provider the origin handed the route to, so counting them shows which transit is really carrying the prefix.
Is the share a measure of traffic?
No. It is the share of routing-table vantage points that prefer each upstream, which is a proxy for reachability and path preference, not a byte count. Real traffic depends on where your visitors are.
Why is one upstream so dominant?
AS path length is a major tiebreaker in BGP best-path selection, and a provider that peers widely offers a short path to a lot of networks. A transit chain that resells through several intermediaries is longer at every vantage point, so it rarely wins.
What is a good AS path length?
There is no target number, but consistency matters for anycast: if your sites sit behind upstreams with very different path lengths, traffic concentrates on the shortest one regardless of geography.