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

Robert Raszuk robert at
Wed Sep 9 15:42:59 UTC 2020

It's not about numbers ... it's about ability to uniformly express policy
with chain of arguments.

See even with large communities you can define a policy with an
unstructured parameter and single action then you need to put it on all of
your boxes to act upon.

Is it possible to perhaps express it there to do what you need today or
what you think is possible today.

Imagine if you would be sending BGP updates between your internal peers and
tell each peer how to read the encoding ... Doable - sure. Good idea - not


On Wed, Sep 9, 2020 at 5:19 PM Mark Tinka <mark.tinka at> wrote:

> On 9/Sep/20 15:25, Robert Raszuk wrote:
> That's not quite true.
> See the entire idea behind defining a common mechanism for signalling
> policy in communities in a flexible way for both intra and inter-domain use
> is to help you to use the same encoding acros policy engines of many
> vendors.
> I would actually risk to say that it could be even more applicable
> intra-domain then inter-domain.
> See the crux of the thing is that this is not just about putting bunch of
> type-codes into IANA reg. It is much more about uniform encoding for your
> actions with optional parameters across vendors.
> In fact the uphill on the implementation side is not because signalling
> new value in BGP is difficult to encode ... it is much more about taking
> those values and translating those to the run time policies in a
> flexible way.
> But how does that scale for vendors? Let me speak up for them on this one
> :-).
> We are now giving them extra work to write code to standardize communities
> for internal purposes. What extra benefit does that provide in lieu of the
> current method where Juniper send 1234:9876 to Cisco, and Cisco sees
> 1234:9876?
> Should a vendor be concerned about what purpose an internal community
> serves, as long as it does what the Autonomous System wants it to do?
> Unless I am totally misunderstanding your goal.
> Mark.
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