Two BGP peering sessions on single Comcast Fiber Connection?

Kraig Beahn kraig at
Mon Oct 17 12:26:39 UTC 2016

Steering clear of the failure domain conversation, if its of any benefit -
we can at least confirm that Comcast is willing to establish /29's for
multiple BGP connections at 56 Marietta/ATL.

These circuits are written on true wholesale/transit IP service contracts,
which may be the difference.

In our experience the Comcast Enterprise/Business groups have rather rigid
circuit provisioning profiles, and even if you are able to talk an engineer
into building a customer's configuration outside of their normal "scope",
it usually comes back to haunt you at some point in the future, even if
years later.

Will send a link to the Comcast enterprise ip transit profiles separately,
for reference, in the event you were not provided such previously...Or if
Comcast wholesale is on the list, of course feel free to chime in too!

On Fri, Oct 14, 2016, 1:49 PM Bill Blackford <bblackford at> wrote:

> It comes down to sizing your failure domain. Any single upstream Transit
> alone means the failure domain is the whole site (making assumptions about
> your topology). As mentioned earlier, any single point of failure doesn't
> reduce your failure footprint and gives little in terms of redundancy. Now
> if you point that second router to a second provider, now you've reduced
> the size of your failure domain to a single router/Transit, not the whole
> site.
> -b
> On Fri, Oct 14, 2016 at 10:34 AM, Paul S. <contact at> wrote:
> > +1, could not have said it better.
> >
> >
> > On 10/15/2016 01:47 AM, Leo Bicknell wrote:
> >
> >> In a message written on Thu, Oct 13, 2016 at 05:48:18PM +0000, rar
> wrote:
> >>
> >>> The goal is to keep the single BGP router from being a single point of
> >>> failure.
> >>>
> >> I don't really understand the failure analysis / uptime calculation.
> >>
> >> There is one router on the Comcast side, which is a single point of
> >> failure.
> >>
> >> There is one circuit to your prem, which is a single point of failure.
> >>
> >> To connect two routers on your end you must terminate the circuit
> >> in a switch, which is a single point of failure.
> >>
> >> And yet, in the face of all that somehow running two routers with
> >> two BGP sessions on your end increases your uptime?
> >>
> >> The only way that would even remotely make sense is if the routers
> >> in question were horribly broken / mismanaged so (had to be?) reboot(ed)
> >> on a regular basis.  However if uptime is so important using gear
> >> with that property makes no sense!
> >>
> >> I'm pretty sure without actually doing the math that you'll be more
> >> reliable with a single quality router (elminiation of complexity),
> >> and that if you really need maximum uptime that you had better get
> >> a second circuit, on a diverse path, into a different router probably
> >> from a different carrier.
> >>
> >>
> >
> --
> Bill Blackford
> Logged into reality and abusing my sudo privileges.....

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