[AusNOG] Going Dual Homed (without waste)

[Mark ZZZ Smith]

----- Original Message -----
> From: Mark Tees <mark.tees at digitalpacific.com.au>
> To: James Mcintosh <james.mcintosh at rocketmail.com>
> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net>
> Sent: Thursday, 26 September 2013 6:14 PM
> Subject: Re: [AusNOG] Going Dual Homed (without waste)
> 
> Hey James,
> 
> Outbound is pretty easy. Check flow data to see which AS's make up your 
> destination traffic or take a punt. Then use BGP local pref to send traffic down 
> the desired BGP session.
> 
> Inbound, can sometimes be influenced by reasonable prepending and adding BGP 
> communities that correspond to local preference in your upstream providers 
> network. This depends on your upstreams.
> 

If you're dual homed to the same provider, a further option to influence inbound is to announce longer prefixes within your aggregates and attach the NO_EXPORT community to them so they don't leave the upstream provider's AS and add to the global route table. The longest match rule will prefer the longer prefixes over the aggregates. For example, announce your /22 over both of your links, as well as /24 from within the /24 over one of the links with NO_EXPORT attached. The /24 link will now be preferred for 1/4 of your /22 space.



> Commercially, Nth percentile will give you the best bang for buck usually in 
> that scenario.
> 
> 
> On 26/09/2013, at 5:52 PM, James Mcintosh <james.mcintosh at rocketmail.com> 
> wrote:
> 
>>  Hi Noggers,
>> 
>>  Somewhat of a follow on from my previous post. I got a lot of comments back 
> saying we should be muti-homed rather than single homed as we currently are.
>> 
>>  I agree, however my question is how do we do so without over-provisioning 
> transit and having too much "waste". If we're currently pumping 
> around 600Mbps of inbound traffic through a single transit provider, how would 
> we equally balance that across two transit providers at 300Mbs each.
>> 
>>  Sure we could advertise some of our IP blocks via transit provider A and 
> other IP blocks via transit provider B but that is hardly my idea of an easy 
> load balancing solution and the traffic levels could still vary dramatically 
> depending on downstream activities.
>> 
>>  Your comments and ideas are much appreciated.
>> 
>> 
>>  -James
>> 
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