>> question for ops:
>> 
>> did you even know this was happening, that "set community" might not
>> replace ALL well known communities?"
>> 
>> the reasom i ask is, as you see in the draft, we are hesitant to
>> propose changing behavior for existing wks as it might impact ops.
>> but if we were not aware of this behavior, then maybe change is ok,
>> in fact desirable.
>> 
>> i did not realize this was going on.  jay, who discovered it, was
>> surprised.
> 
> NTT noticed this type of inconsistency between some vendors somewhere
> in July 2016. A customer used a combination of NTT-specific BGP
> communities to influence traffic, together with
> NO_ADVERTISE. Unbeknownst to us, this combination of communities
> resulted in network behavior that made the customer happy.
> 
> Further down the timeline, the customer was migrated to another
> vendor's routing platform (or got a new circuit on a new platform,
> don't recall) and suddenly noticed that the previously working
> combinatory trick no longer worked. At that point investigation showed
> that "set community" does not do the same thing on all platforms, and
> we had to figure out a way to make things consistent.
> 
> Our currently routing policy is to allow (not delete) some of the
> well-known communities, and squash (remove) a bunch of
> not-so-well-know communities and unsupported well-known communities,
> and let potential-future-well-known communitie pass-through to try to
> not stiffle innovation. For each new well-known community we'll have
> to decide whether to remove it or let it pass-through.

not sure if you and/or your customer(s) would be made unhappy if current
behavior in some vendor(s), where "set" does not remove some wkcs, was
changed to remove all.

randy

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