BGP Community - AS0 is de-facto "no-export-to" marker - Any ASN reserved to "export-only-to"?'

Mike Hammett nanog at
Tue Sep 8 18:35:51 UTC 2020

How I see the OP's intent is to create a BCP of what defined communities have what effect instead of everyone just making up whatever they draw out of a hat, simplifying this process for everyone. 

Mike Hammett 
Intelligent Computing Solutions 


----- Original Message -----

From: "Tom Beecher via NANOG" <nanog at> 
To: "Douglas Fischer" <fischerdouglas at> 
Cc: "NANOG" <nanog at> 
Sent: Tuesday, September 8, 2020 1:30:19 PM 
Subject: Re: BGP Community - AS0 is de-facto "no-export-to" marker - Any ASN reserved to "export-only-to"?' 

BGP Large Communities ( ) already provides for anyone to define the exact handling you wish. 

On Tue, Sep 8, 2020 at 11:57 AM Douglas Fischer via NANOG < nanog at > wrote: 

Most of us have already used some BGP community policy to no-export some routes to some where. 

On the majority of IXPs, and most of the Transit Providers, the very common community tell to route-servers and routers "Please do no-export these routes to that ASN" is: 

-> 0:<TargetASN> 

So we could say that this is a de-facto standard. 

But the Policy equivalent to "Please, export these routes only to that ASN" is very varied on all the IXPs or Transit Providers. 

With that said, now comes some questions: 

1 - Beyond being a de-facto standard, there is any RFC, Public Policy, or something like that, that would define 0:<TargetASN> as "no-export-to" standard? 

2 - What about reserving some 16-bits ASN to use <ExpOnlyTo>:<TargetASN> as "export-only-to" standard? 
2.1 - Is important to be 16 bits, because with (RT) extended communities, any ASN on the planet could be the target of that policy. 
2.2 - Would be interesting some mnemonic number like 1000 / 10000 or so. 


Douglas Fernando Fischer 
Engº de Controle e Automação 

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