BGP Looking Glass
A BGP looking glass for any IP or prefix: see the AS-paths, peer counts and origin AS observed from 23 RIPE RIS route collectors worldwide, with a warning when more than one AS originates it.
About BGP Looking Glass
The BGP Looking Glass shows how a given IP address or prefix is reached from outside your own network. Enter an address or a CIDR block and, for every RIPE RIS route collector that sees the route, you get the number of peers currently observing it, the shortest AS-path length, and the best AS-path with the origin AS highlighted. It answers the question a single traceroute cannot: who announces this address space, and does the rest of the internet agree about it.
BGP-4, specified in RFC 4271, has no central routing table. Every router selects its own best path per prefix, and AS-path length is only one tiebreaker in that decision process, so two networks can legitimately reach you by very different routes. The condition worth watching for is MOAS, multiple origin AS: two or more autonomous systems originating the same prefix. Anycast deployments and some multi-homing arrangements do this deliberately, but so does a route hijack, where another operator announces your address space and pulls traffic towards their own AS.
The data comes from 23 RIPE NCC RIS route collectors at major internet exchanges - Amsterdam, London, Frankfurt, Geneva, Milan, Barcelona and Bucharest in Europe, plus Dubai, Miami, Johannesburg and Montevideo among others - so the European view is well represented rather than an afterthought. When more than one origin AS appears, a MOAS warning is raised above the table, and expanding a collector lists every peer's full AS-path so you can judge the announcement yourself. Queries run server-side from our EU infrastructure. Nothing is returned for a prefix that is unannounced, or more specific than what RIS peers carry.
How to use it
- 1Enter an IP address or a prefix in CIDR notation, or click the example network to load one.
- 2Select Query looking glass to fetch the current view from the RIS collectors.
- 3Read the summary cards: collectors reporting, total observing peers, how many origin ASes were seen, and which AS numbers announce the prefix.
- 4If a MOAS warning appears, check whether the extra origin AS is one you recognise as your own anycast or multi-homed setup.
- 5Scan the collector table for the peer count, shortest path length and best AS-path at each exchange, with the origin AS highlighted.
- 6Click any collector row to expand it and inspect every peer's full AS-path from that vantage point.
Common use cases
- -Confirming a new prefix is visible worldwide after you announce it for the first time or move it to a new upstream.
- -Investigating a suspected route hijack when a second autonomous system starts originating your address space.
- -Troubleshooting reachability complaints from one region by comparing AS-paths at the collector nearest the affected users.
- -Auditing how many of your upstreams actually propagate your announcement, and how long the AS-paths towards you are.
- -Planning a peering or transit change by seeing which transit ASes appear in the paths towards a target prefix today.
Frequently asked questions
- What is a BGP looking glass?
- A looking glass is a read-only window into the BGP routing table as seen by a router or route collector elsewhere on the internet. It shows which AS originates a prefix and the AS-path other networks use to reach it. This one reads 23 RIPE RIS collectors at internet exchanges worldwide, so you compare many vantage points at once instead of one router's view.
- What does MOAS mean in BGP?
- MOAS stands for multiple origin AS: the same prefix is announced by more than one autonomous system at the same time. It is legitimate for anycast services and for some multi-homed setups where two ASes originate the same block. It is also the signature of a route hijack, so any unexpected origin AS should be checked against the covering ROA and against the address holder's intent.
- Why is my prefix not visible in the looking glass?
- There are three common reasons: the prefix is not being announced at all, an upstream is filtering it, or it is more specific than the routes RIS peers carry. IPv4 announcements longer than /24 and IPv6 announcements longer than /48 are widely filtered and often absent everywhere. Query the covering less-specific block; if that is visible, the aggregate is carrying your traffic.
- Is a looking glass the same as a traceroute?
- No. A looking glass shows the control plane, meaning the AS-path a network has chosen and advertised in BGP, while traceroute shows the data plane, the routers packets actually traverse. Routing is often asymmetric, so the return path can differ from the AS-path shown here. Use the looking glass to establish who announces a prefix and how, and traceroute to find where packets stop.