Follow up question on "next hop self"

[Ondrej Zajicek]

On Mon, Jan 06, 2020 at 06:25:30PM +0000, Neil Jerram wrote:
> On Sun, Dec 22, 2019 at 3:03 PM Ondrej Zajicek <santiago at crfreenet.org>
> wrote:
> 
> > On Sat, Dec 21, 2019 at 12:39:43AM +0100, Nico Schottelius wrote:
> > > I have had a look at OSPF, but for our relatively simple network it
> > > looks like an overkill. Do you have any other recommendations for
> > > what to run the IGP with instead?
> > >
> > > The main reason I so far tried to stay on iBGP only is to reduce
> > > complexity.
> >
> > Well, you can run just IBGP, if you use direct + 'next hop self' options,
> > which should be OK in your simple topology.
> >
> 
> According to my understanding of the BIRD code, 'next hop self' is only
> relevant when exporting a locally originated route to a BGP peer.  So,
> assuming the original question was about what happens on R1 and R2, I would
> not expect it to be relevant at all.   Is that right?

Option 'next hop self' is relevant in both exporting locally originated
route to a BGP (i.e. a route without existing bgp_next_hop attribute) and
exporting route from BGP to another BGP (i.e. a route with existing
bgp_next_hop attribute).

See bgp_use_next_hop() and bgp_use_gateway() functions and their usage.

-- 
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."