Comment by geocar
4 days ago
> This isn't how BGP works
This is exactly how BGP works.
https://bgplabs.net/policy/7-prepend/
> Leaking a new route isn't going to magically make some other route become more preferred.
Not magic, but technology can look like magic when you don't understand it.
> > > That's presumptuous: A state actor would (and could trivially) pad the wrong directions to flow traffic down to pops that are not making new announcements
> > Leaking a new route isn't going to magically make some other route become more preferred.
> Not magic, but technology can look like magic when you don't understand it.
Please let me know of the scenario where route A is preferred, undesirable, long-path route B is advertised/leaked, and as a result traffic flows over route C.
I've used BGP for over 25 years, so I'm really curious what you're thinking. Or if you're describing something else, you're being really unclear.
Or if you're just describing withdrawing a route and replacing it with a really undesirable route -- sure, we do that all the time. But that doesn't match this scenario and isn't going to get flagged as a routing anomaly.
> https://bgplabs.net/policy/7-prepend/
You know what's really toxic? Not explaining what you mean and just sending some introductory lab documentation about what the other person has already clearly shown they understand.
I don't even know what you mean by a lot of these things.. e.g.
> > > As soon as I peer with two big sites that don't peer directly with each-other, they both gotta let me forward announcements unfiltered across them.
A straightforward reading of "forward" doesn't work for this sentence. I should not take a route from peer A and send it to peer B. Peering isn't transitive. If I try, it should be filtered.
Peering means to give your own routes (and your transit customers' routes) to someone else. Not your other peers routes.
> Please let me know of the scenario where route A is preferred, undesirable, long-path route B is advertised/leaked, and as a result traffic flows over route C.
> ... I'm really curious what you're thinking
That the actor actually wanted the traffic to flow over route C.
> You know what's really toxic? Not explaining what you mean and just sending some introductory lab documentation about what the other person has already clearly shown they understand.
I think perhaps you and I have different ideas of what is "clear", for example when you said something that is totally covered in introductory lab documentation, I thought it was clear that you did not understand.
> I don't even know what you mean by a lot of these things
That is clear! But confusing! How can you clearly understand but not know what I mean?
> Peering means to give your own routes (and your transit customers' routes) to someone else.
That's exactly what's happening here: Not every transit customer peers with every other transit customer.
> > Please let me know of the scenario where route A is preferred, undesirable, long-path route B is advertised/leaked, and as a result traffic flows over route C.
Yes, but how does advertising undesirable route B make traffic go over route C? This is why I think you're confused.
> That's exactly what's happening here: Not every transit customer peers with every other transit customer.
I am not understanding what you're saying at all. You said:
> > > > As soon as I peer with two big sites that don't peer directly with each-other, they both gotta let me forward announcements unfiltered across them.
This is the thing you are supposed to never do as a peer, and the thing that I have a whole bunch of filtering to prevent my peers from inadvertently doing.
Are you misusing the word "peer"? It's hard to talk about BGP and routing policy without using these words correctly.
I think I'm going to give up here.
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