[AusNOG] Vocus prefix issue

[Lincoln Dale]

On Tue, Oct 24, 2023 at 12:54 AM Steven Waite <Steven.Waite at comtel.com.au>
wrote:

> I hope all is well. It’s been a very busy few weeks since the wonderful
> event at SeaWorld. Just hoping if someone from Vocus shoot me an off list
> email about a multi homing issue we are having. Would seem Vocus is taking
> longer then expected to drop a /24 prefix from there routing table that was
> advertise by our ASN via TPG. We are advertising /23 two both carriers and
> the high and low /24 separately between Voucs and TPG with each service
> backup each other. Would seem Vocus holds onto the TPG /24 while most other
> ASN drop it when we have an outage allowing /23 to take effect but Vocus
> does not clear the /24 thus preventing routing back to Vocus via the /23.
> Not super urgent
>

What are your expectations on how fast the greater-internet will see the
prefix flip-flop in case of failure?
Because even in the best case, it's likely multiple minutes, as the default
BGP MRAI in many implementations is not zero seconds.  It's also unlikely
you can do anything to influence that, as you don't control the
configuration of devices in ASNs other than your own.

Now of course you probably want to nail down whatever TPG/Vocus do with
your prefixes/how they announce them, or post on here what the prefixes are
so there's more data to go on, but I suspect it's more nuanced than you
think it is.
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