Re: What's up with BGP communities?

[John Fraizer via NANOG <nanog () lists nanog org>]

Read RFC1997 and RFC1998 for more info n depth understanding of communities
and their value/use.

--
John Fraizer
LinkedIn profile: http://www.linkedin.com/in/johnfraizer/




On Thu, Jan 22, 2026 at 5:02 PM William Herrin via NANOG <
nanog () lists nanog org> wrote:

> On Thu, Jan 22, 2026 at 1:55 PM Ronan Pigott <ronan () rjp ie> wrote:
> > IIUC, a "route map" is a configuration local to the BGP router. So, an
> > operator may make some decision about the meaning of a community and then
> > attach it to routes advertised to their peers, but no peer can reasonably
> > act on the community information without understanding the meaning
> intended
> > by the owner, right?
>
> Correct.
>
> > So if I operated a network and my BGP peer advertises
> > routes that belong to a bunch of communities, how can I possibly learn
> the
> > intended meaning of those communities to configure a sensible route map
> for
> > my router?
>
> You ask your peer. In some cases, the peer writes a web page which
> explains what their communities mean so that they can just say, "look
> at this web page." And then you have sites like bgp.tools which
> collect the information from the various web pages individual networks
> have published into a large database.
>
> Because the communities have arbitrary meanings, those meanings are
> communicated person to person, not machine to machine.
>
> Regards,
> Bill Herrin
>
>
> --
> For hire. https://bill.herrin.us/resume/
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