[j-nsp] Avoid transit LSPs

[Luis Balbinot]

Yes it can, but it won't scale. There are lots of PE routers with the same
situation.

I was expecting for a simple configuration knob to avoid detour LSPs but
there seems to be none.

Breaking the OSPF areas could be an option but I don't see anything working
differently if I export the TED via BGP to those routers as the CSFP would
find its way through those routers once again.

Today I don't have any issues because all PE routers are using tunneled
LDP. But since there's no flexibility on how we can control which FEC takes
each tunnel I'm having to extend RSVP all the way to the PEs.

Luis

On Tue, 29 Jan 2019 at 07:03 <adamv0025 at netconsultings.com> wrote:

> > From: Luis Balbinot <luis at luisbalbinot.com>
> > Sent: Monday, January 28, 2019 1:39 PM
> >
> > I have many LSPs from P1 to P4 and all have FRR protection (Juniper FRR,
> 1:1).
> > Even with two distinct paths from P1 to P4 (both with much lower IGP
> > metrics) I get some detour LSPs setup on PE1. PE1 is a low-end ACX5k with
> > very limited transit capabilities and I definitely don't want any
> transit traffic
> > through it.
> >
> > I could color the green links and call them "p-pe" for example but I
> can't just
> > exclude all "p-pe" links from the FRR selection. If I setup an LSP from
> P1 to
> > PE1 the CSPF path will be P1->P2->PE1 and I'll need the P1->P2->P3->PE1
> > path for protection, but that can't be setup because it has a "p-pe"
> member
> > in the path.
> >
> > P2->PE1 and P3->PE1 share the same fate as P2->P3, but even with SRLG
> > it is not guaranteed that LSPs won't be setup over the PE1 circuits.
> >
> I think what could be done in this topology is to mark the P2-PE1 and
> P3-PE1 links with special colour (say green for the sake of this example).
> 1) Now as for the RSVP-TE signalled LSPs between P routers (e.g. between
> P1 and P4)
> Those would be set up to exclude green colour when signalling their detour
> LSPs.
> [edit protocols mpls label-switched-path LSP_P1_TO_P4]
> set fast-reroute exclude GREEN
> 2) only LSPs to PE1 will have no such constrain configured for their
> detour LSPS.
> And thus will be able to use the P2-PE1 and P3-PE1 links in order to
> protect the last leg of the path towards PE1
>
> adam
>
>
>