Timeline for The relationship between IP address and AS number
Current License: CC BY-SA 4.0
20 events
| when toggle format | what | by | license | comment | |
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| Feb 14, 2023 at 12:29 | comment | added | Teun Vink | What you're saying is correct. You may have meant this the whole time, but were using wrong terms like multihoming and aggregation to describe it. | |
| Feb 14, 2023 at 2:09 | comment | added | wyb |
@TeunVink, thanks a lot for your help. I lack hands-on experience, which makes my ideas may be just possible in theory. In the case above, I thought Google has more than one upstream ASes. Level3 receives /24 from Google and its other downstream ASes. So Level3 makes the /9 super-prefix and advertises /9. At the same time, Google advertises its own 8.8.8.0/24 to other upstream ASes, making 8.8.8.0/24 also in the global routing table. If this is impractical, please just let me know and I won't pursue it any further.
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| Feb 13, 2023 at 14:42 | comment | added | Teun Vink | No, the /24 is not multihomed. Prefixes can't be multihomed, ASNs can be. What you MAY mean, is that there are multiple origins for the /24, for which the correct term is 'anycasted'. That is not the case here, only one ASN (Google) is announcing the /24. Level3 is announcing the /9, but since more specific routes win from less specific routes, traffic will get routed to Google. | |
| Feb 13, 2023 at 14:14 | comment | added | wyb | @TeunVink, could you please explain further? I think the AS originating that /24 may be multi-homed, making that /24 also in the routing table. (Sorry to have disturbed you for so long. But I could not find any BGP details on Google.) | |
| Feb 13, 2023 at 13:20 | comment | added | Teun Vink | But it's not an aggregation, since the /24 is also in the routing table. It is a less specific route, but that's not the same as aggregation. | |
| Feb 13, 2023 at 11:28 | comment | added | wyb |
@TeunVink, I do find that /9 in a BGP Routing Table project - thyme.panic.net. It’s path is [2516 3356(Level3)].
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| Feb 13, 2023 at 10:43 | comment | added | Teun Vink | Route aggregation is irrelevant here, since you're looking at routing registries, not routing tables. The /9 is assigned to Level3. They allocated that /24 to Google to use for. 8.0.0.0/9 IS assigned to one organisation (Level3) and can be originated by only that organisation. Parts of that /9 were assigned to other networks. | |
| Feb 13, 2023 at 10:33 | comment | added | wyb |
@TeunVink, I search a lot based on your answer, and there are some statements I’d like to know whether they’re right. Level3 is allowed to advertise 8.0.0.0/9 and It is the origin AS of this prefix. Due to the subnet 8.8.8.0/24 advertised by another AS Google, we can infer that Level3 makes a route aggregation here. But Level3 can not be marked as the origin in Route Object, if 8.0.0.0/9 is not owned by just one organization.
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| Feb 12, 2023 at 5:45 | comment | added | wyb | @RonMaupin, I’m sorry to mix everything up. I don’t know how to describe the public ip addresses of the devices within an AS, which we can visit through the Internet. I incorrectly thought “these ip addresses are owned by the original AS”. | |
| Feb 12, 2023 at 5:20 | vote | accept | wyb | ||
| Feb 12, 2023 at 3:58 | comment | added | Ron Maupin♦ | @wyb Yes, but that is not an internal use of an address, which is what you asked about. Internally, the AS could have that server or anything else addressed differently. Also, understand that IANA owns all the IP addressing, and it authorizes the RIRs to assign addressing it has assigned to each RIR to other companies (not only ISPs). | |
| Feb 12, 2023 at 3:34 | comment | added | wyb |
@RonMaupin, thanks so much for your patience. Assume that there is a web server connected to a router of AS E. The IP address of the web server is 1.2.3.4 and we can visit it through the Internet. Isn't 1.2.3.4 authorized to use by its owner?
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| Feb 12, 2023 at 2:54 | comment | added | Ron Maupin♦ | @wyb, "the public IP addresses used by network devices within an AS are authorized by the IP address owners, and it has nothing to do with the entity owning the AS." No. You are again trying to tie completely different concepts. The addressing used inside an AS can be any addressing the AS owner wants to use. No outside entity can dictate how networking is done inside an AS, and that is the entire point of an AS (the ."A" is for Autonomous). | |
| Feb 12, 2023 at 2:41 | comment | added | wyb | @RonMaupin so the public IP addresses used by network devices within an AS are authorized by the IP address owners, and it has nothing to do with the entity owning the AS. Sometimes they(IP and ASN) are owned by the same entity. Is that right? And how can we get the public IP addresses used by network devices within an AS? | |
| Feb 11, 2023 at 19:25 | comment | added | Teun Vink | In addition to what Ron said, an ASN can also announce prefixes belonging to another (downstream) ASN. | |
| Feb 11, 2023 at 19:14 | comment | added | Ron Maupin♦ | @wyb, "can we say these IP prefixes form the AS?" No. You are confusing two different concepts. AS (Autonomous System) only means that the entity with the AS is autonomously managed; it can do what it likes within its own network. An AS can, or not, advertise prefixes to other ASes, and that really has nothing to do with the IP prefixes that may be assigned to an entity that has an AS. The DoD has several very large prefixes assigned to it, but does not advertise some, so other ASes may use those internally, and the DoD has authorized outside ASes to advertise some of them. | |
| Feb 11, 2023 at 13:28 | comment | added | wyb | Perhaps I was not very clear. If an ISP registers some IP prefixes and an AS number to provide service, can we say these IP prefixes form the AS? I thought "the prefixes owned by an AS" refer to the network devices' ip addresses in that AS. @TeunVink | |
| Feb 11, 2023 at 12:49 | comment | added | Teun Vink | Like I said: prefixes aren’t owned by an ASN, they’re owned by an organization and can be announced by one or more ASNs. | |
| Feb 11, 2023 at 11:23 | comment | added | wyb | Got it! Then how can we get all IP prefixes owned by a specific AS through official public information on BGP? | |
| Feb 11, 2023 at 9:06 | history | answered | Teun Vink | CC BY-SA 4.0 |