Networks ignoring prepends?

Mon Jan 22 21:26:33 UTC 2024

On Mon, Jan 22, 2024 at 1:11 PM Andrew Hoyos <hoyosa at gmail.com> wrote:
> On Jan 22, 2024, at 14:35, William Herrin <bill at herrin.us> wrote:
>> The best path to me from Centurylink is: 3356 1299 20473 11875
>
>> The path Centurylink chose is: 3356 47787 47787 47787 47787 53356
>> 11875 11875 11875
>
>> Do you want to tell me again how that's a reasonable path selection,
>> or how I'm supposed to pass communities to either 20473 or 53356 which
>> tell 3356 to behave itself?
>
> AS53356 (Free Range Cloud Hosting) appears to have some limited BGP communities that may help.
> https://docs.freerangecloud.com/en/bgp/communities
>
> implies that you sending 53356:19014 would block announcements to 47787.

At which point Centurylink chooses 40676 7489 11875 11875 11875 11875
11875 11875 11875.

> This certainly seems like a reasonable path selection, in the context that 47787 is likely a 3356 customer.

That's -why- 3356 chooses the paths. 40676 and 47787 are customers,
1299 is a peer. You're telling me with a straight face that you think
that's *reasonable* routing?

> That may turn into a game of whack a mole, but the knobs appear to be there to try something other than prepending to influence 3356’s selection.

Whack-a-mole is not a reasonable solution to anything.

Besides, I don't want to drop the path to 53356 via 47787. If the path
through 20473 fails, the path through 53356 is the next best and I
want Centurylink to use it.

Regards,
Bill Herrin

-- 
William Herrin
bill at herrin.us
https://bill.herrin.us/