[j-nsp] improving global unicast convergence (with or without BGP-PIC)

[Dragan Jovicic]

As mentioned on mx trio indirect-nh is enabled and can't be disabled.
You could check with > show krt indirect-next-hop protocol-next-hop
commands (0x3 flag should mean it is enabled).
However this was not the case in older Junos versions where
indirect-next-hop was in fact not enabled and had to be enabled even on mx
mpc (it escapes me when was this, pre-13 or so).

If your uplink fails, with indirect-nh change is almost instantaneous,
given your BGP next-hop is unchanged, as only one pointer needs to be
rewritten (or you have equal cost uplinks...). However you still need
composite-next-hop feature for L3VPN labeled traffic and this is NOT
enabled by default (might be important if you run lots of routes in vrf)...

If your BGP next-hop changes and you have routes in rib (add-paths,
advertise-external, multiple RRs....), and you have them installed in FT
(pre- or post- 15.1), you still rely on failure detection of upstream BGP
router or upstream link (even slower, but you could put upstream links in
IGP).

There's also egress-protection for labeled traffic..

Before we implemented bgp pic/add-paths, we used multiple RR and iBGP mesh
in certain parts and spread BGP partial feeds from multiple upstream
routers to at least minimize time to update FIB, as none of this required
any upgrade/maintenance.

If you find your FIB update time is terrible, bgp pic edge will definately
help..

BR,


-Dragan

ccie/jncie





On Tue, Apr 18, 2017 at 10:07 PM, Vincent Bernat <bernat at luffy.cx> wrote:

>  ❦ 18 avril 2017 21:51 +0200, Raphael Mazelier <raph at futomaki.net> :
>
> >> Is this the case for chassis MX104 and 80? Is your recommendation to run
> >> with indirect-next-hop on them as well?
> >>
> >
> > Correct me if I'm wrong but I think this is the default on all the MX
> > since a long time. There as no downside afaik.
>
> Documentation says:
>
> > By default, the Junos Trio Modular Port Concentrator (MPC) chipset on
> > MX Series routers is enabled with indirectly connected next hops, and
> > this cannot be disabled using the no-indirect-next-hop statement.
> --
> Harp not on that string.
>                 -- William Shakespeare, "Henry VI"
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