[j-nsp] Optimizing the FIB on MX

[Dragan Jovicic]

Advertise-external or more general Additional Path capability (would prefer
this if new install) could be used to distribute selected few routes if FIB
space is of concern.

One thing I haven't seen mentioned is that routers need indirect-nexthop
feature enabled, which should be by default enabled on recent Junos
versions on all-MPC chassis. Otherwise, change of core interface will take
at least a couple of dozen seconds to update FIB. DPC cards do not support
this, and on older version you'd need to enable this feature by hand, if i
remember correctly.

Also, if this protection is used in l3vpn, you would optimally need
composite-nexthop feature which decouples link between indirect-nexhop and
outer label (which is changed once core link fails).


Regards

On Fri, Feb 19, 2016 at 11:02 AM, Adam Vitkovsky <Adam.Vitkovsky at gamma.co.uk
> wrote:

> > Alexander Marhold [mailto:alexander.marhold at gmx.at]
> > Sent: Thursday, February 18, 2016 6:50 PM
> >
> > Hi folks
> >
> > To make the discussion clearer and comming back to the Juniper MX 104
> > implementation
> >
> > Here is a picture of 2 PEs on P  and 2 peers (ISP1 and IX1) let´s assume
> we
> > want to prefer routes from IX1 over ISP1
> > MX1 is EBGP (lpref 100) to  ISP1 and IBGP to MX2 and MX3
> > MX2 is EBGP (lpref 110) to IX1 and IBGP to MX1 and MX3
> >
> >   ISP1                   IX1
> >     | locpref         ^ locpref
> >     |   100              |   110
> >    MX1--------->-MX2
> >     |                               |
> >     |                               |
> >     +------MX3--->--+
> >
> >
> > In my opinion if you need also  the MX3 then  for this MX3 you need "PIC-
> > CORE" to quickly switch between both paths
> >
> Yes that's right, "protect core" under routing-options of the Internet VRF.
>
> However then I can ask what if MX2 fails or is severed from the core
> completely,
> though with that I'd be opening a whole different and very interesting
> realm of convergence options.
> First you'd need to tune your IGP so it propagates the unreachability of
> MX2's loopback towards MX3 as fast as possible.
> Then I could argue that MX3 is in a different AS and it knows about MX2's
> loopback via BGP-LU -so you'd need to tune BGP-LU infrastructure(can't
> shave of much delay).
> Then I could argue I want sub 50ms convergence in the above case and well
> then, then you'd have to rely on P routers to perform the local repair and
> swing from MX2 to MX1 If MX2 goes down.
> And that brings me to Segment Routing and protecting a node segment upon
> the failure of its advertising node
>
>
> > On MX1 you need "best-external" to advertise the external routes whereas
> > the best is the internal route pointing to MX2
> >
> > On MX1 and MX2 you need "PIC-EDGE" to quickly switch when IX1 goes
> > down
> >
> Well technically you need PIC-EDGE only on MX2 so it can do the local
> repair for traffic destined to IX1 and re-label it so that it gets to MX1.
>
> > Do we all agree on that picture and the named mechanisms ( put in "") ?
> >
> >
> > So now what versions of Junos is needed and what additional "unnecessary"
> > methods like MPLS or LDP is now needed ?
> >
> Well I'm afraid you'd need to run MPLS L3VPNs for all this.
>
>
> adam
>
>
>         Adam Vitkovsky
>         IP Engineer
>
> T:      0333 006 5936
> E:      Adam.Vitkovsky at gamma.co.uk
> W:      www.gamma.co.uk
>
> This is an email from Gamma Telecom Ltd, trading as “Gamma”. The contents
> of this email are confidential to the ordinary user of the email address to
> which it was addressed. This email is not intended to create any legal
> relationship. No one else may place any reliance upon it, or copy or
> forward all or any of it in any form (unless otherwise notified). If you
> receive this email in error, please accept our apologies, we would be
> obliged if you would telephone our postmaster on +44 (0) 808 178 9652 or
> email postmaster at gamma.co.uk
>
> Gamma Telecom Limited, a company incorporated in England and Wales, with
> limited liability, with registered number 04340834, and whose registered
> office is at 5 Fleet Place London EC4M 7RD and whose principal place of
> business is at Kings House, Kings Road West, Newbury, Berkshire, RG14 5BY.
>
>
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
>