[quagga-dev 11704] Re: [PATCH] zebra: Connected route addition shoudn't happen in MRIB

Everton Marques everton.marques at gmail.com
Thu Oct 30 13:34:40 GMT 2014


On Thu, Oct 30, 2014 at 10:36 AM, David Lamparter <
david at opensourcerouting.org> wrote:

> On Thu, Oct 30, 2014 at 10:04:58AM -0200, Everton Marques wrote:
> > On Thu, Oct 30, 2014 at 5:17 AM, Balaji G <balajig81 at gmail.com> wrote:
> > > On Thu, Oct 30, 2014 at 12:25 PM, David Lamparter <
> > > david at opensourcerouting.org> wrote:
> > >> On Thu, Oct 30, 2014 at 11:55:28AM +0530, Balaji G wrote:
> > >> > On Thu, Oct 30, 2014 at 10:40 AM, David Lamparter <
> > >> > david at opensourcerouting.org> wrote:
> > >> > > This patch was discussed on IRC between Balaji, Everton and me;
> the
> > >> > > outcome was that Balaji would resend it with a switch to control
> the
> > >> > > behaviour.
> > >> > >
> > >> >
> > >> > I would send a V2 with that switch. do you want something
> "rib-lookup
> > >> > mrib". On executing this the connected routes and the RPF check is
> made
> > >> in
> > >> > the MRIB and executing "no rib-lookup mrib" would bring it back to
> URIB
> > >> > lookup and remove the connected routes. Would that be fine ?
> > >>
> > >> Hm, we have 3 cases:
> > >> 1. MRIB only
> > >> 2. MRIB first, then URIB
> > >> 3. URIB only
> > >>
> > >> Options 1. and 3. can be "emulated":
> > >> 1. = use 2. but install add "default unreachable" route to MRIB
> > >>      => URIB lookup never happens
> > >> 3. = use 2. but leave MRIB empty
> > >>      => empty MRIB doesn't get used
> > >>
> > >
> > > Thanks for the suggestion but i guess we can have two in terms of CLI.
> > > MRIB-URIB and URIB .
> > >
> > > MRIB-URIB Case:This would be with MBGP and Mroute enabled where the
> > > look-up happens at the MRIB first and then URIB. The connected routes
> would
> > > be installed in MRIB and URIB
> > > URIB Only- No MRIB and No routes get installed in MRIB including
> Connected
> > > Routes
> > > MRIB Only - Not sure if this is needed in CLI
> > >
> >
> > I would like to know if there is a case for MRIB only as well.
>
>
> So... why MRIB-only?  Because URIB-only and MRIB-only are the easy to
> understand variants where you don't need to figure out which exact way
> of combining the URIB and MRIB the router is using.  A complicated
> mode is a good way unexpected things to happen...
>

Ok, it makes sense.


>
> (btw.  Which MRIB+URIB mixing variants exactly are you going with?  The
> old Cisco, the new Cisco, or something else?  Or more than one?)
>

I do not have a strong preference on any.

I think the whole picture could be summarized in the following steps
(higher priority first):

1) connected is not installed in MRIB by default

2) default MRIB-URIB mixing:

- lookup MRIB by longest match; if route found, skip URIB lookup
- if MRIB route not found, lookup URIB by longest match

3) add specific cli knob to disable RPF lookup against MRIB

4) add specific cli knob to disable RPF lookup against URIB

5) add specific cli knob to inject connected into MRIB

6) add specific cli knob to change the MRIB-URIB mixing for
modern-cisco-like:

- query both MRIB by longest match (if cli enabled) and URIB by longest
match (if cli enabled)
- resolve MRIB vs URIB:
  -- longest match wins
  -- ties are resolved by administrative distance

What do you think?

Everton
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