algorithm used by (RIPE region) ISPs to generate automatic BGP prefix filters

Pavel Odintsov pavel.odintsov at gmail.com
Thu Feb 4 12:13:48 UTC 2016


Hello!

You could check awesome project for this purposes:
http://www.stableit.ru/2015/06/generate-bgp-filters-with-bgpq3.html
It's authored by Russian carrier RETN.net.

On Thu, Feb 4, 2016 at 2:58 PM, Henrik Thostrup Jensen <htj at nordu.net> wrote:
> Hi Martin
>
> On Thu, 4 Feb 2016, Martin T wrote:
>
>> am I correct that ISPs (in RIPE region), who update their BGP prefix
>> filters automatically, ask their IP transit customer or peering
>> partner to provide their "route"/"route6" object(s) or "as-set" object
>> in order to find all the prefixes which they should accept?
>
>
> This is a common practice to do. Both within and outside the RIPE region.
> For bigger networks, prefix lists become somewhat unwieldy, and one can then
> use as-path filters instead. Use a prefix limit with this.
>
> Typically you use a tool (bgpq3) to generate the prefix lists.
>
>> If the IP transit customer or peering partner provides an "as-set", then
>> ISP needs to ensure that this "as-set" belongs to this IP transit customer
>> or peering partner because there is no automatic authentication for this,
>> i.e. anybody can create an "as-set" object to database with random "members"
>> attributes?
>
>
> I don't know the procedure for creating as-sets, maybe someone else can chip
> in.
>
>> This is opposite to "route"/"route6" objects which follow a strict
>> authentication scheme.
>
>
> I believe this differs depending on the irrd software/operator.
>
>> In addition, in case of "as-set", an ISP needs to recursively find all the
>> AS numbers from "members" attributes because "as-set" can include other
>> "as-sets"?
>
>
> Some irrd servers, can expand this automatically (I think). But seriously,
> use a tool for this.
>
>> Quite a lot of question, but I would simply like to be sure that I
>> understand this correctly.
>
>
> There are basically two abstractions:
>
> 1. as-set. Can contain other as-sets or as numbers.
> 2. prefixes are registered to an as-number.
>
> Remember that there are multiple IRR servers, and they mirror each other.
>
> Use http://irrexplorer.nlnog.net/ to play around a bit :-).
>
>
>     Best regards, Henrik
>
>  Henrik Thostrup Jensen <htj at nordu.net>
>  Software Developer, NORDUnet
>
>



-- 
Sincerely yours, Pavel Odintsov


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