Policy-based routing is evil? Discuss.

Fri Oct 11 17:41:46 UTC 2013

On Oct 11, 2013, at 10:27 AM, William Waites <wwaites at tardis.ed.ac.uk> wrote:

> I'm having a discussion with a small network in a part of the world
> where bandwidth is scarce and multiple DSL lines are often used for
> upstream links. The topic is policy-based routing, which is being
> described as "load balancing" where end-user traffic is assigned to a
> line according to source address.
> 
> In my opinion the main problems with this are:
> 
>  - It's brittle, when a line fails, traffic doesn't re-route

it's brittle

>  - None of the usual debugging tools work properly
>  - Adding a new user is complicated because it has to be done in (at
>    least) two places
> 

you take all the useful information that an IGP could be (or is) providing you, and then you ignore it and do something else.

> But I'm having a distinct lack of success locating rants and diatribes
> or even well-reasoned articles supporting this opinion.
> 
> Am I out to lunch?

evil is not a synonym for ugly patch placed over a problem that could be handled better. If it's being used as an alternative to VRF, it isn't.

> 
> -w
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.

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