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BGP Prefix Lookup

Enter a prefix (or a single address). Answered from our daily copy of the global routing table.

Examples:

121.242.0.0/16

One collector's view (APNIC). A route filtered before it reaches that collector is not listed.

Announced exactly

Registry
APNIC · India · Aug 14, 2006
Delegated block
121.240.0.0 – 121.247.255.255

Covering routes

0

No less-specific route covers it.

More-specific routes

79 more-specifics from 3 origin AS(es)

On the internet, routes are announced as prefixes: an autonomous system tells its neighbours via BGP that it can deliver traffic for, say, 193.166.0.0/15. This tool looks a prefix up in our daily copy of the global routing table and shows three things:

  • Exact announcements: which AS originates exactly this prefix. More than one origin (a MOAS) is normal for anycast services and some multihomed networks, and suspicious otherwise.
  • Covering routes: less-specific announcements that contain it. Traffic follows the most specific route, so a covering route matters if the more-specific one disappears.
  • More-specifics: announcements inside it, which may belong to other networks (customers, or a hijack).

Each announced route is also checked against the RPKI: whether a ROA authorises its origin AS.

The table is the view from APNIC’s route collector. Most of the global table is the same from everywhere, but a route that is filtered before it reaches that collector will not appear.

Frequently asked questions

Why is my /24 not listed but a /16 is?

Your addresses are announced as part of the larger block, and no one announces the /24 separately. That is the normal case for most customers of a provider.

What is a more-specific hijack?

Someone announces a longer prefix inside your space. Because routers prefer the most specific route, traffic goes to them. RPKI with a strict max length makes such announcements invalid.

Can I enter a single address?

Yes. The tool then shows the most specific announced route that contains it.

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