I am a bit confused.
I would like to know since when a current ASN (and its corresponding prefixes) have been in place.
When I look at the example at team-cymru (http://www.team-cymru.com/IP-ASN-mapping.html) I see:
$ whois -h whois.cymru.com " -v 126.96.36.199 2005-12-25 13:23:01 GMT" AS | IP | BGP Prefix | CC | Registry | Allocated | Info | AS Name 23028 | 188.8.131.52 | 184.108.40.206/24 | US | arin | 1998-09-25 | 2005-12-25 13:23:01 GMT | TEAMCYMRU - SAUNET You may also query for some basic AS information directly: $ whois -h whois.cymru.com " -v AS23028" AS | CC | Registry | Allocated | AS Name 23028 | US | arin | 2002-01-04 | TEAMCYMRU - SAUNET
So, the ASN
23028 and it BGP prefix
220.127.116.11/24 have been allocated in 1998 or in 2002?
The netblock the IP address 18.104.22.168 is in was originally allocated on 1998-09-24.
The autonomous system number 23028 was registered on 2002-01-04.
Their registration dates have no relation to each other, nor is there any reason for them to. IP netblocks and AS numbers are independent. Routes can change at any time. So can ASNs.
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.