best practice for advertising peering fabric routes

Patrick W. Gilmore patrick at
Wed Jan 15 15:57:02 UTC 2014

On Jan 15, 2014, at 10:44 , William Herrin <bill at> wrote:
> On Tue, Jan 14, 2014 at 10:11 PM, Patrick W. Gilmore <patrick at> wrote:

>> NEVER EVER EVER put an IX prefix into BGP, IGP, or even
>> static route. An IXP LAN should not be reachable from any
>> device not directly attached to that LAN. Period.
>> Doing so endangers your peers & the IX itself. It is on the order
>> of not implementing BCP38, except no one has the (lame,
>> ridiculous, idiotic, and pure cost-shifting BS) excuse that they
>> "can't" do this.
> Hi Patrick,
> I have to disagree with you. If it appears in a traceroute to
> somewhere else, I'd like to be able to ping and traceroute directly to
> it. When I can't, that impairs my ability to troubleshoot the all too
> common can't-get-there-from-here problems. The more you hide the
> infrastructure, the more intractable problems become for your
> customers.
> The IXP LAN should be reachable from every device on the ASes which
> connect to it, not just the immediate router.

We disagree.

Plus, you really can't type "ping" on the router connected to the IXP?

_If_ you can guarantee your network has zero bots, abusable [DNS|NTP|etc.] servers, all your downstreams are perfectly clean, etc., etc., then maybe I could see you carrying it in your IGP.

As I know 100% of ISPs (to at least one decimal place) cannot make such a guarantee, then doing so puts the IXP and all other members - whether peers of yours or not - at risk. Putting others at risk because you are lazy or because it makes your life easier is .. I believe I called it bad manners before.

But let's take the philosophical out of this. The prefix in question is owned by the IXP. I said in an earlier post that if you carry a prefix I own, did not announce to you, and make it very clear I specifically do not want you to carry, I will ask you to stop or face possible disconnection. You may claim convergence (a bit of BS), troubleshooting (non-issue, IMO), or even "but I waaaaaaaaaaaant to!!1!1!" (whatever). Doesn't matter. That's not your prefix, you were not given it and told not to carry it, so Do Not Carry It.

Ask your IXP if they mind whether you carry the prefix. See what they say.


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