[AusNOG] Attempting to understand DC internet connectivity

[Joseph Goldman]

If you look at BGP best path selection (on Cisco at least) Local Pref 
has always come before BGP AS Path, and it would be silly for any 
provider to not local pref downstream customers first. Your only other 
choice on this front would be to have an external system monitoring your 
primary path, and actively bringing up/destroying the BGP session with 
your backup path when required, however I'd say this is more prone to error.

On 14/04/15 14:07, Richard Thornton wrote:
> Thanks Mark, I remember seeing that in the past and thinking it was 
> dodgy that they were modifying/ignoring my prepends, looking at the 
> best way to add resiliency at minimum cost.
>
> On Tue, 14 Apr 2015 at 13:58 Mark Newton <newton at atdot.dotat.org 
> <mailto:newton at atdot.dotat.org>> wrote:
>
>
>     On Apr 14, 2015, at 10:57 AM, Richard Thornton
>     <richie.thornton at gmail.com <mailto:richie.thornton at gmail.com>> wrote:
>
>     > Thanks Harry, so would you do something like 20mbit with Vocus
>     and 1mbit with Telstra on a high speed port burstable to 20mbit
>     and basically set the local preference and AS prepends to always
>     use Vocus when it is up?
>
>     No, Telstra will localpref any prefixes you send them, so the
>     Telstra link will carry all the traffic to you from AS1221 and
>     AS4637 even when the Vocus link is up.
>
>     So you’ll likely need more than 1 Mbps commit to Telstra if you
>     have any capacity to them at all.
>
>     What are you actually trying to achieve, in business terms? Cost
>     reduction? Resiliency? Something else?
>
>        - mark
>
>
>
>
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