Two BGP peering sessions on single Comcast Fiber Connection?

Bill Blackford bblackford at
Fri Oct 14 17:48:35 UTC 2016

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


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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