Regarding source based outbound routing (with redundancy)

Sat Oct 5 18:55:09 UTC 2013

On Oct 5, 2013, at 11:43 AM, Christopher Morrow <morrowc.lists at gmail.com> wrote:

> On Sat, Oct 5, 2013 at 2:08 PM, joel jaeggli <joelja at bogus.com> wrote:
>> 
>> On Oct 5, 2013, at 9:45 AM, Christopher Morrow <morrowc.lists at gmail.com> wrote:
>> 
>>> you really don't want to do policy routing :(
>>> 
>> 
>> PBR has this tendency to be brittle in the face of topology changes.
> 
> yup, exactly my point :(
> 
>> There are much better way to outbound load-balance between providers offering same or similar quality routes to the same destination.
>> 
>> multi-AS multipath will do that if the peers are on the same router. BGPaddpath
>> can do it for you if the peers are spread across routers.
> 
> these both will require seeing the longer prefix from the right peer
> though, right? and selecting that would just be like natural selection
> anyway…

so at this level if I can install two best paths in the fib then great I'll just hash flows between them… this does nothing for source based path selection but it does a lot for load-balancing between peers especially if there's substantial overlap of equidistant paths. If you have say 2914/3356 and you look at the amount of traffic that you can load-balance between them instead of simply tie-breaking on router-id or however far do your path algorythm you get, it's significant enough to matter.

> yikes, I suppose you could:
>  1) generate the longer prefix internally
>  2) set it's next-hop to something reachable out both (all) peers
>  3) metric the preferred peer's next-hop appropriately
>  4) profit
> 
> but that sounds also kind of messy and prone to odd failures when
> changes are made :(

I go for the low hanging fruit, which is better usage of the information I already have.

> you'd be adding complexity that you'd have to track through the life
> of your network :( (and explain to anyone 'not you' working on the
> network)
> 
> -chris
> 
>> joel
>> 
>>> On Sat, Oct 5, 2013 at 12:19 PM, Anurag Bhatia <me at anuragbhatia.com> wrote:
>>>> Hello there!
>>>> 
>>>> 
>>>> I am trying to do a source based outbound routing between multiple
>>>> upstreams. Usually I picked outbound via localpref but here I wish to use
>>>> Provider 1 for say 10.10.10.0/24 while provider 2 for small chunk of it say
>>>> 10.10.10.0/28. I wish to keep failover support and thus so if provider 2
>>>> fails, I wish to push traffic again via Provider 1.
>>>> 
>>>> Is this is possible only with VRF or I can push for some specific match
>>>> rule in route maps?
>>>> 
>>>> 
>>>> 
>>>> Thanks.
>>>> 
>>>> --
>>>> 
>>>> 
>>>> 
>>>> Anurag Bhatia
>>>> anuragbhatia.com
>>>> 
>>>> Linkedin <http://in.linkedin.com/in/anuragbhatia21> |
>>>> Twitter<https://twitter.com/anurag_bhatia>
>>>> Skype: anuragbhatia.com
>>> 
>> 
> 

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