On Tue, Apr 18, 2017 at 04:50:41PM +0000, Michael Hare wrote:
> Hello,
>
> Sorry if this is an easy question already covered. Does anyone on list have
> an understanding of what happens in the FIB in the following circumstance?
>
> Simplified topology;
> * Router 1 RIB default points to reject
> * Router 1 RIB has default free feed from attached eBGP neighbor A
> * Router 1 RIB has default free feed from attached iBGP neighbor B (add-path)
>
> I guess what I'm trying to understand, from the perspective of improving
> upstream convergence for outbound packets from our AS, if my default route
> pointed to a valid next hop of last resort am I likely to see an improvement
> (reduction) in blackholing on router 1 during topology changes? The thought
> being that if Router 1 FIB invalidates next-hop A quickly (en masse) packets
> could match default route with valid next-hop while FIB is being
> re-programmed with more specifics via B?
>
> I am aware of indirect-next-hop being default on MPC but my understanding is
> this will not work for directly connected eBGP peers? So if session with A
> drops (BFD, link, whatever) are routes with next hop to neighbor A
> deprogrammed nearly atomically due to some level of indirection or are routes
> considered one by one until all routes (~600K) have been processed? I
> suspect the latter but perhaps looking for verification.
You want to set indirect-next-hop in all use-cases. This allows
faster FIB convergence upon RIB events because all shared next-hops can be
updated
at once.
> I am aware of BGP PIC but not yet running 15.X [when internet is not in VRF].
> I am willing to accept that if BGP PIC is the best approach to improving
> this scenario an upgrade is the best path forward. I'd be curious to hear
> from anyone who is on 15.1 [or newer] and using MPC4 in terms of perceived
> code quality and MPC4 heap utilization before/after.
Since you are running a full RIB+FIB, you want to leverage PIC & INH to
get the full performance feasible from your hardware.
- Jared
--
Jared Mauch | pgp key available via finger from [email protected]
clue++; | http://puck.nether.net/~jared/ My statements are only mine.
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