How to enter static prefix with multiple nexthops but no ECMP?

[Ondrej Zajicek]

On Wed, Oct 16, 2019 at 02:52:10PM +0000, Kenth Eriksson wrote:
> On Wed, 2019-10-16 at 16:43 +0200, Ondrej Zajicek wrote:
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> > 
> > On Wed, Oct 16, 2019 at 01:41:45PM +0000, Kenth Eriksson wrote:
> > > Hi!
> > > 
> > > Does bird support a static prefix with multiple nexthops, without
> > > installing all of them in the kernel as ECMP?
> > 
> > Hi
> > 
> > I think that you are talking about multiple routes/paths with the same
> > prefix. Static protocol currently does not support that (and behaves
> > strangely when such multiple routes are defined). Simple workaround
> > is to define multple static protocol instances. We have a patch for
> > multiple static routes with the same prefix and different preference
> > in one static protocol (commit 9861dba5230da539e6ce7d2b6baa4f2631556d09),
> > but we plan to rewrite that significantly before merging to master.
> > 
> 
> Ok, thanks for clarifying that. What is the target release for that
> feature?

Probably something like 2.0.8-9.

The design of our protocol-table interface requires that if i have
multiple routes with the same networks, there must be an u32 value
that distinguishes them (that is inspired by BGP ADD-PATH design).

In the patch above we used preference for this distinguisher, but later
we got some feedback that it may be more useful to have IGP-comparable
metric (i.e. igp_metric attribute) for this (so multiple routes with
the same preference and different igp_metric can be used). Another
possibility is to have separate 'id' argument for distinguisher unrelated
to any real attribute, but that may be inconvenient for users. Yet another
possibility is to have some automatic 'id' assignment based on all static
route attribute through hash table, but that seems like a too much /
unnecessary work.

So i would like to get some feedback w.r.t. that.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."