[AusNOG] steering inbound BGP (Telstra)

[Andrew Jones]

The option of advertising a /23 through Telstra, and the two 
more-specific /24s through your preferred supplier would work, because 
the most specific route will always take precedence.

BGP itself does support what Chris wants to do, but it would require 
Telstra allowing customers to set a community to indicate that the route 
learned should be less-preferred than their peer and transit routes. 
Like Ben said, by default most providers will give higher preference to 
customer routes.

Andrew

On 17.02.2014 14:15, Joshua D'Alton wrote:
> I could be wrong but BGP just doesn't support what you're wanting,
> and even more so no carrier is ever really going to work in the way
> you describe. It should never make sense (for a carrier) to not 
> prefer
> their own routes (which are directly connected, ie admin dist 1), vs
> those of their peers (even if settlement free, admin dist 1+N), even
> if communities were involved (i believe telstra do use communities
> internally between telstra/telstraglobal/reach).
>
> Even if you advertised /24s telstra would still use their own learned
> routes (from you) rather than peer learned routes (from your 
> alternate
> upstream), as designed BGP.
>
> I don't know for sure it is default behaviour for TWI, but I believe
> it is default for... the internet in general.
>
> I think the only way to achieve what you want would be to engineer
> the system such that nothing is advertised to telstra, and only
> advertised if the other link goes down. I can think of a few ways to
> do this, but keeping in mind BGP announce times, it wouldn't be a 
> 100%
> uptime.
>
> Good luck with the traffic engineering, there are definitely a few
> onlist that are experts.
>
> On Mon, Feb 17, 2014 at 1:59 PM, Chris Gibbs
> <Chris.Gibbs at gosford.nsw.gov.au> wrote:
>
>> Hey all,
>>
>> We currently utilise Telstra Internet Direct services for our 
>> primary inbound for AS38236, I would like to move to using Telstra as 
>> the least preferred and swap to another provider for inbound.
>>
>> When I tested the swap, the majority of domestic looking glasses 
>> were confirming inbound through our preferred inbound. However Telstra 
>> always seems to prefer their own routes instead of peer learnt; even 
>> after setting either as-prepend or MED. A Telstra engineer confirmed 
>> this.
>>
>> My question is pretty much is there any other way to steer inbound 
>> traffic to us through Telstra? (without grabbing a /23 and advertising 
>> more specific 2 x /24s or using communities, which Telstra doesn't 
>> support)
>>
>> The only other alternative would be to swap providers at our DR 
>> site, and we originally had issues getting a service installed there.
>>
>> Does anyone also know if this is the default behaviour through 
>> Telstra Wholesale Internet?
>>
>> Cheers ,
>>
>> [1]
>>
>> Chris Gibbs
>> Network and Security Engineer | Information Management & Technology
>> Gosford City Council
>> (PO Box 21)
>> Gosford NSW 2250
>> P (02) 43258888
>> M 0408 222 496
>> E Chris.Gibbs at gosford.nsw.gov.au
>>
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