Allowas-in in BIRD - possible to implement?
Hello, I am in dire need to accept my own AS in AS-PATH from my upstream provider. Is there any way to achieve it using bird? Regards -- Adrian Czapek
--On 30 June 2011 11:38:53 +0200 Adrian Czapek <adrian.czapek@rybnet.pl> wrote:
I am in dire need to accept my own AS in AS-PATH from my upstream provider. Is there any way to achieve it using bird?
A key element of BGP loop prevention is not doing this. Wanting to do this suggests to me your BGP design is wrong or you are using the wrong solution for the job. Complete guess: are you trying to survive when your AS becomes partitioned? If so, the easy way (given you say "provider") is simply to carry around an IGP or BGP default route pointing at said provider. -- Alex Bligh
A key element of BGP loop prevention is not doing this.
I am fully awared of it.
Wanting to do this suggests to me your BGP design is wrong or you are using the wrong solution for the job.
Complete guess: are you trying to survive when your AS becomes partitioned? If so, the easy way (given you say "provider") is simply to carry around an IGP or BGP default route pointing at said provider.
Indeed, I want to survive AS split. And I must say that this default route is very simple solution and i will gonna use it. However, accepting own AS in AS-PATH could be handy too. Cisco can do it, Quagga can do it too, it would be good to have it in bird. Of course, it must be turned off by default and you have to know what are you doing when enabling it. When everything is all right, you have to take care that your internal path is always choosen. When AS is splitted, it will simply route through internet, just like your 'default route' does. Default route might not be such effective when you have more then one upstream provider, since you have to choose default route throu one of them, and if you have bad luck and both internal connection and this particular provider will fail at the same time, you're toasted. Regards -- Adrian Czapek
--On 1 July 2011 13:47:50 +0200 Adrian Czapek <adrian.czapek@rybnet.pl> wrote:
Default route might not be such effective when you have more then one upstream provider, since you have to choose default route throu one of them, and if you have bad luck and both internal connection and this particular provider will fail at the same time, you're toasted.
So, the standard solution here is originate the default route(s) conditionally. In OSPF you can tie them to the interfaces going up and down (which doesn't help much if the session dies). In BGP that's harder if I remember correctly, but there was a Cisco knob I used a while ago; I'm afraid I forget which. A more serious problem is that if your AS is partitioned, you need to have routes to subnets of your summary/aggregate block unless your aggregate block's numbering divides well with the partition. Even accepting own AS is not in general a fix here because the routes tend to be too long to avoid filtering by the upstream. As there is not a lot of traffic here (but what there is is important), sometimes tunnels work. -- Alex Bligh
On Thu, Jun 30, 2011 at 11:38:53AM +0200, Adrian Czapek wrote:
Hello, I am in dire need to accept my own AS in AS-PATH from my upstream provider. Is there any way to achieve it using bird?
See http://permalink.gmane.org/gmane.network.bird.user/944 -- Elen sila lumenn' omentielvo Ondrej 'SanTiago' Zajicek (email: santiago@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
participants (3)
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Adrian Czapek -
Alex Bligh -
Ondrej Zajicek