[j-nsp] remove-private for iBGP session

[Cydon Satyr]

Hello,

I'm very well aware of that which is why I'm confused.
Here, PE is removing private AS before sending update to RR.

Could anyone explain what are we missing here?

Regards

On Sun, Sep 27, 2015 at 6:09 PM, Adam Vitkovsky <Adam.Vitkovsky at gamma.co.uk>
wrote:

> Hello Cydon,
>
> > Of Cydon Satyr
> > Sent: Saturday, September 26, 2015 12:35 PM
> >
> > Hello,
> >
> > I was under the impression that remove-private works for eBGP sessions,
> as
> > it does on Cisco routers (if my memory serves me right).
> >
> > But I notices that remove-private on a PE router would remove private AS
> > (from customer's vrf bgp session) before sending it to a route reflector.
> >
> > Is this normal behavior, or I'm missing something?
> >
> > Regards
>
> It's not normal according to the RFC4271 section 5.1.2.a
>
> 5.1.2.  AS_PATH
>
> >snip
>
>    When a BGP speaker propagates a route it learned from another BGP
>    speaker's UPDATE message, it modifies the route's AS_PATH attribute
>    based on the location of the BGP speaker to which the route will be
>    sent:
>
>       a) When a given BGP speaker advertises the route to an internal
>          peer, the advertising speaker SHALL NOT modify the AS_PATH
>          attribute associated with the route.
>
>       b) When a given BGP speaker advertises the route to an external
>          peer, the advertising speaker updates the AS_PATH attribute as
>          follows:
>
> >snip
>
> There are other attributes (e.g. MED springs to mind) that can't be
> modified or set on iBGP sessions.
>
>
> For iBGP to iBGP (on a RR)
> On XR you can modify all attributes only when cmd "ibgp policy out
> enforce-modifications"
> Because by default:
> In addition, when a RR reflects a route, it SHOULD NOT modify the
>    following path attributes: NEXT_HOP, AS_PATH, LOCAL_PREF, and MED.
>    Their modification could potentially result in routing loops.
>
>
> adam
>
>
>         Adam Vitkovsky
>         IP Engineer
>
> T:      0333 006 5936
> E:      Adam.Vitkovsky at gamma.co.uk
> W:      www.gamma.co.uk
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