nanog mailing list archives
Re: What's the point of prepend communities?
From: Brett Frankenberger <rbf+nanog () panix com>
Date: Thu, 26 Oct 2017 14:52:07 -0500
On Thu, Oct 26, 2017 at 03:05:25PM -0400, William Herrin wrote:
You'd only use communities like that if you want to signal the ISP to deprioritize your advertisement on a particular peer or set of peers but not others. That's when you're getting fancy. It's not the norm. The norm is you want to deprioritize one of your paths as a whole. Maybe that link has less capacity or is enough better connected that it would always override your other links unless you detune it a little. I mean, you could tell the ISP to prepend everything based on a community, assuming they support such a community, but why would you? That needlessly makes things more complicated.
Completely agree. I would add that some providers' "prepend everything" community is really "prepend to all peers" (or something else shy of "prepend to every BGP neighbor we have"). In that case, if the customer prepends, the prepend is seen by the provider's other customers, but if the customer sets the "prepend to all peers" community, the provider's customers won't see the prepend. There are cases where that functionality would be useful. I have never seen a provider with a true "prepend to every BGP neighbor we have" community, but it might well exist somewhere. -- Brett
Current thread:
- What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? Christopher Morrow (Oct 26)
- Re: What's the point of prepend communities? Job Snijders (Oct 26)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? Rob Foehl (Oct 28)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- RE: What's the point of prepend communities? Naslund, Steve (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- Re: What's the point of prepend communities? Brett Frankenberger (Oct 26)
- Re: What's the point of prepend communities? Steve Dodd (Oct 28)
- Re: What's the point of prepend communities? Leo Bicknell (Oct 26)
- Re: What's the point of prepend communities? Clinton Work (Oct 26)
- RE: What's the point of prepend communities? Naslund, Steve (Oct 26)
- Re: What's the point of prepend communities? Leo Bicknell (Oct 30)
- Re: What's the point of prepend communities? Michael Hallgren (Oct 30)
- Re: What's the point of prepend communities? Mike Hammett (Oct 29)
- Re: What's the point of prepend communities? Brett Frankenberger (Oct 29)