[AusNOG] Going Dual Homed (without waste)

[Mark ZZZ Smith]

----- Original Message -----
> From: Mark ZZZ Smith <markzzzsmith at yahoo.com.au>
> To: Mark Tees <mark.tees at digitalpacific.com.au>; James Mcintosh <james.mcintosh at rocketmail.com>
> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net>
> Sent: Friday, 27 September 2013 7:07 AM
> Subject: Re: [AusNOG] Going Dual Homed (without waste)
> 
> 
> 
> 
> 
> ----- 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.

Should have been "as well as /24 from within the /22 over one of the links".

Also, you'll need to attach NO_EXPORT as you announce the route via eBGP to the upstream AS. If you attach it within your network/AS, your router won't announce the route via eBGP because it has been told to NO_EXPORT it.

> 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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>>>   AusNOG at lists.ausnog.net
>>>   http://lists.ausnog.net/mailman/listinfo/ausnog
>> 
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