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Re: IP Prefixes are allocated ..
>>>>> "Glen" == Glen Kent <[email protected]> writes: Glen> to different Autonomous systems. No. Wrong. IP addresses are allocated to network providers, or to end-user networks. The recipient of a block of IP addresses (by direct allocation/assignment from ARIN or by a PI assignment from some other registry) can get their provider to announce the block, in which case the AS number will change any time they change providers, or indeed they can get several providers to announce parts of the block. Or they can choose to get an AS number of their own and announce it themselves. They might announce part of it themselves and have a provider announce other parts, and so on. There is no fixed relationship between addresses and ASNs. Glen> Is there a central/distributed database somewhere that can tell Glen> me that this particular IP prefix (say x.y.z.w) has been given Glen> to foo AS number? To find out what AS is actually announcing a given IP address, the place to look is in the routing tables themselves, or information services which draw their data from routing tables. One such is whois.cymru.com: % whois -h whois.cymru.com 184.108.40.206 ASN | IP | Name 11697 | 220.127.116.11 | NET-SUPERNEWS - Supernews Another is the asn.routeviews.org DNS zone: % host -t txt 0.0.168.216.asn.routeviews.org. 0.0.168.216.asn.routeviews.org text "11697" "18.104.22.168" "19" Both of these tell you who _IS_ announcing the space, not who _SHOULD BE_ announcing it. Routing registries such as RADB tell you another story; they tell you who _thinks_ that they _should_ be announcing it or allowing it to be announced. The quality of such data is poor at best; often it is nonexistent. Never trust the RADB data to be either correct or complete. There is currently no fully reliable way for a third party to answer the question "should AS N be announcing prefix X". The history of netblock thefts shows that even network providers have a hard time answering the question "should my customer C be announcing prefix X". -- Andrew, Supernews http://www.supernews.com