[j-nsp] Optimizing the FIB on MX

[Adam Vitkovsky]

> sthaug at nethelp.no [mailto:sthaug at nethelp.no]
> Sent: Thursday, February 18, 2016 11:13 AM
>
> Just commenting on a couple things:
>
> > If the MX140-A from our previous example loses its Transit link it
> > will (via BGP-PIC) immediately reroute traffic to MX140-B However by
> default MX140-B has a best path via MX140-A -so until it receives withdrawn
> from MX140-A it'll loop traffic back to MX140-A.
> > That's why you want MX140-B to prefer it's local exit.
> >
> > *not sure what was Juniper and ALU thinking when they came up with the
> same protocol preference for eBGP and iBGP routes, there's a ton of reasons
> why you always want to prefer closest AS-EXIT.
>
> Probably the same as Cisco, when Cisco on multiple occasions have
> promoted using the same administrative distance (200) for both EBGP and
> IBGP as "best practice".
>
Well the bottom line is the sanity won.


> > Caveats:
> > "vrf-table-label" must be enabled at the routing-instance on the
> > MX140s - just another stupidity in this script kiddie OS of Junos
>
> You are of course free to call JunOS whatever you want. Calling JunOS a
> "script kiddie OS" may not the best way to be taken seriously.
>
> In any case, vrf-table-label is *much* older than PIC (around 10 years, if I
> remember correctly).
>
And that makes vrf-table-label a prerequisite for PIC?
My point is that if a packet is received with a VRF label the label points to an indirect next hop pointer
And the pointer points to a forwarding next-hop i.e.  IP edge-interface and adjacent L2 rewrite
and as a backup could point to an MPLS core-interface and adjacent label stack (NH label to backup PE(if any) and VRF label that backup PE advertised)
-basically an ASBR option B label swap operation
Why would I need to run an unnecessary IP lookup in the VRF table to derive info about the backup path?

adam








        Adam Vitkovsky
        IP Engineer

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