Yes, sometimes very much so, and often nice to combine with local-pref settings
based on upstream's "geo-community-values" when available.
Cheers,
mh
Le 1 nov. 2017 à 18:59, à 18:59, Leo Bicknell a écrit:
>In a message written on Mon, Oct 30, 2017 at 07:56:43PM +0100,
In a message written on Mon, Oct 30, 2017 at 07:56:43PM +0100, Michael Hallgren
wrote:
> But keep in mind that 'prepend communities' are fragile: I decide by local
> preference whereto I send my traffic.
Absolutely, but they are still very useful in many situations.
--
Leo Bicknell -
Hi guys,
But keep in mind that 'prepend communities' are fragile: I decide by local
preference whereto I send my traffic.
Cheers,
mh
Le 30 oct. 2017 à 18:25, à 18:25, Leo Bicknell a écrit:
>In a message written on Thu, Oct 26, 2017 at 01:54:17PM -0600, Clinton
>Work wrote:
In a message written on Thu, Oct 26, 2017 at 01:54:17PM -0600, Clinton Work
wrote:
> I believe that Jason is asking about an ISP BGP community to prepend
> their AS when the BGP routes are received from the customer (not when
Yeah, I typoed my example, should have been:
There are paths:
1 2 3
On Sun, Oct 29, 2017 at 07:01:13AM -0500, Mike Hammett wrote:
> If I understand the OP correctly, I will use this real world example:
>
> https://onestep.net/communities/as174/
>
> 174:3001 through 174:3003 as compared to doing the prepending
> yourself. What is the functional difference?
>
<jason+na...@lixfeld.ca>
To: "William Herrin" <b...@herrin.us>
Cc: "NANOG" <nanog@nanog.org>
Sent: Thursday, October 26, 2017 1:47:44 PM
Subject: Re: What's the point of prepend communities?
Hi Bill,
> On Oct 26, 2017, at 2:37 PM, William Herrin <b...@her
On Thu, 26 Oct 2017, Jason Lixfeld wrote:
Absolutely. I understand the "Prepend to Network blah” use case. The case I
don’t get is where the ISP makes no distinction in their policy document about how
the prepending of their own AS is applied to their upstream announcements, implying
that
Keep in mind also that when you allow a customer to deprioritize a
particular peer you can really blow up your COGS model (assuming you buy
transit).
Cheers,
Steve
On Thu, Oct 26, 2017 at 1:05 PM, William Herrin wrote:
> On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld
On 10/26/17 10:58, Jason Lixfeld wrote:
> Hi,
>
> Of all the ISPs that I am familiar with that have a BGP community structure
> usable by their peering partners and/or downstream customers, among other
> things, they allow the customer to signal the ISP to prepend their own AS to
> the as-path
Sent: Thursday, October 26, 2017 2:54 PM
To: nanog@nanog.org
Subject: Re: What's the point of prepend communities?
I believe that Jason is asking about an ISP BGP community to prepend their AS
when the BGP routes are received from the customer (not when
advertising to a peer). I don't see
I believe that Jason is asking about an ISP BGP community to prepend
their AS when the BGP routes are received from the customer (not when
advertising to a peer). I don't see a functional difference between
the two and I suspect that ISPs added support for convenience. If you
already send BGP
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
-
From: NANOG [mailto:nanog-boun...@nanog.org] On Behalf Of William Herrin
Sent: Thursday, October 26, 2017 2:15 PM
To: Jason Lixfeld
Cc: NANOG
Subject: Re: What's the point of prepend communities?
On Thu, Oct 26, 2017 at 3:05 PM, William Herrin <b...@herrin.us> wrote:
> On Thu, Oct
In a message written on Thu, Oct 26, 2017 at 02:47:44PM -0400, Jason Lixfeld
wrote:
> I understand how prepends fit in the context of best path selection, but my
> question was more the difference between a customer signalling the ISP to
> prepend their AS using a BGP community stamped to a
On Thu, Oct 26, 2017 at 3:05 PM, William Herrin wrote:
> On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld
> 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
> On Oct 26, 2017, at 2:55 PM, Job Snijders wrote:
>
> If Network B offers some kind of “Prepend to Network C” BGP community,
> network A will be able to utilize all of network B except the pieces that
> perform less well. (This is ofcourse assuming that Network C picks some
>
On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld
wrote:
> Hi Bill,
>
> > On Oct 26, 2017, at 2:37 PM, William Herrin wrote:
> >
> > BGP routing is based on "distance". Distance in BGP is primarily
> calculated as the number of ASNs in the AS Path. Prepends
Hi,
In context of traffic engineering it may be that Network A (customer of
Network B) observes that performance is suboptimal between Network B and
Network C.
If Network B offers some kind of “Prepend to Network C” BGP community,
network A will be able to utilize all of network B except the
On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld
wrote:
> Hi Bill,
>
> > On Oct 26, 2017, at 2:37 PM, William Herrin wrote:
> >
> > BGP routing is based on "distance". Distance in BGP is primarily
> calculated as the number of ASNs in the AS Path. Prepends
Hi Bill,
> On Oct 26, 2017, at 2:37 PM, William Herrin wrote:
>
> BGP routing is based on "distance". Distance in BGP is primarily calculated
> as the number of ASNs in the AS Path. Prepends make a path more distance,
> encouraging routers to choose a different path if one is
On Thu, Oct 26, 2017 at 1:58 PM, Jason Lixfeld
wrote:
> Of all the ISPs that I am familiar with that have a BGP community
> structure usable by their peering partners and/or downstream customers,
> among other things, they allow the customer to signal the ISP to prepend
>
Hi,
Of all the ISPs that I am familiar with that have a BGP community structure
usable by their peering partners and/or downstream customers, among other
things, they allow the customer to signal the ISP to prepend their own AS to
the as-path of a particular prefix announcement.
What
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