[quagga-dev 11707] Re: [PATCH] zebra: Connected route addition shoudn't happen in MRIB

David Lamparter david at opensourcerouting.org
Fri Oct 31 03:42:43 GMT 2014


On Thu, Oct 30, 2014 at 11:34:40AM -0200, Everton Marques wrote:
> On Thu, Oct 30, 2014 at 10:36 AM, David Lamparter <
> david at opensourcerouting.org> wrote:
> > (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

If I understand their docs, "modern cisco" seems to be:
  u_best = longest(urib)
  m_best = longest(mrib)
  best = u_best.distance < m_best.distance ? u_best : m_best

(no longest match check between urib and mrib, I think)

> What do you think?

I'd combine knobs 3, 4 and 6 into one knob, like:
  ip rpf-lookup urib-only
  ip rpf-lookup mrib-only
  ip rpf-lookup mrib-before-urib
  ip rpf-lookup mrib-urib-longest
  ip rpf-lookup mrib-urib-distance

I don't have an opinion on what mixing options exactly should be in the
list, I just think one knob makes sense for setting the overall mode.
Option names above are just examples.  Anyway, a single knob to set the
mode for RPF seems easiest to understand for the admin.  (And it keeps
the number of knobs lower.)


-David




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