I'm really confused. I have a list of all the AS numbers and their "description", which I got from MaxMind. I thought the ASN system was pretty straightforward, but let me show you my confusion.

Take AS30058 for example, belonging to FDC Servers: http://bgp.he.net/AS30058. So you would assume that that is the complete list of IPs controlled by that company.

But now look at the huge AS1744, belonging to Congent Communications: http://bgp.he.net/AS174#_prefixes ... there are many many ranges defined there, with the description "FDCservers.net" there too, that were not part of AS30058. So we can assume that they belong to FDCservers.net too, right?

Could it be the case that these ranges were handed back to the ISP/owner/whatever, and their info just has not been updated as they have not been re-used yet?

Also note that if you click on one of those IP ranges,

So, can someone explain the reasoning behind this sort of thing? What is the point of that? Also, is there a way for me to find out all possible IP ranges that belong to a company like FDCservers.net, or some sort of whois query?

I am just trying to get a better understanding of how all this works.

1 Answer 1


You need to think of the difference between IP Range "Announcement" vs Origin AS. So from the perspective of what Hurricane Electrics AS6939 sees announced from its Peers. If you look at the Whois Tab information you will see the "Origin" AS.
To really answer your question though, how do you find out Who really owns WHAT. The arin whois lookup will tell you. Check the link below for all of FDCServers AS30058



  • Thanks. I can use arin to verify this. could you elaborate a bit on announcements, what they're for, and what a peer's job is? Ultimately I'd love to understand Hurricane Electrics shows many FDCServers in that list and not FDC's own AS. I've seen the same data listed the same elsewhere too... Remember, I'm a network noobie here so every little bit of info would be hugely appreciated!
    – ConorD55
    Commented Aug 23, 2014 at 22:43
  • Well, Looking at the v4 graph on HE would be a good place to start. Each AS passes reachability info of the ASs it can reach. AS30058 announces the routes it has in its network & passes those routes to its Peers. AS174 would pass on that it can reach AS30058 to its Peers & so on & so on. Just remember that you're looking at the internet through the eyes of HE. If you were to go to routeserver.org these providers give telnet access to 'look' at their bgp routes from their perspective. The best way to learn BGP would be to start getting some books or check out. bgp4.as
    – LucentMoon
    Commented Aug 23, 2014 at 22:51
  • Ok -- starting to make sense, thanks. So it looks like the only true way to get this info is to whois the respective RIR server's whois on a particular AS, to find out all IP ranges associated with that AS...? Checking out your links now too, thanks.
    – ConorD55
    Commented Aug 23, 2014 at 23:07
  • Seems like my understanding of what an ASN was was totally incorrect. I thought the "prefixes" were ranges which that "belonged" to an ASN. But now I know there isn't any ranges associated with an ASN. The OWNER of an ASN, however, would have IP ranges assigned to them. So to figure out who owns what from an AS, you must figure out who the owner is and look them up otherwise. Could you confirm my new understanding?
    – ConorD55
    Commented Aug 23, 2014 at 23:36
  • ASNs and ip ranges are assigned by IANA I believe. I wouldnt use the word owned per say. the regional internet authority assigned ip ranges to an organization such as an ISP and then that isp can re-allocate to one of its customers. Ip ranges can be traced back to an ORIGIN AS that means. The organization/AS that announced the range/prefix. An ASN is really just an arbitrary number so that The bgp protocol can use as a loop prevention mechanism & identifier for which range/prefixes originate from and the path back to the origin network
    – LucentMoon
    Commented Aug 23, 2014 at 23:45

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