Kevin Dorrell, CCIE #20765

05 Mar 2008

NMC Lab 10 Redistribution

Filed under: Redistribution — dorreke @ 05:59

 Here is my redistribution scheme for Lab 10:

Lab 10 Redistribution

Looking at the diagram, there do not seem to be any active feedback paths, so I should get away without having to tag or filter.  The routing domains are in a straight line:

EIGRP 200 <–> EIGRP 100 <–> OSPF <–> RIP

There are three active border routers, show by the arrows: CAT1, CAT2, and R1.  As there are no active feedback paths, they should not require any special treatment.  There are a further three passive border routers: R2, R3, and R6.  I can adjust the Administrative Distances at those, to ensure optimal routing.

Looking at R2, here are the priorities:

  • 90 = (default) EIGRP 200 internal prefixes
  • 110 = (default) OSPF internal prefixes
  • 120 = (configured) OSPF external prefixes from R1 only.  Practically, all the RIP prefixes.
  • 170 = (default) EIGRP externals.  Practically Lo102, Lo105, EIGRP 100 prefixes
  • 180 = (configured) other OSPF externals.  Practically, this could only be EIGRP 100 prefixes coming back through OSPF, and then only if CAT1 or R5 fails.

I know the scenario does not ask to repair the EIGRP 200 prefixes if CAT1 or R5 fails, but I reckon it’s easier to slap a penalty on them rather than filter them on R2.  I think I can achieve that on R2 like this:

router ospf 10 
  distance ospf external 180 
  distance 120

Now for R3 and R6.  These are identical.  The first thing I notice is that they will perfer the OSPF routes to anything else.  The prefix is OK, because it is firmly “connected” on both R3 and R6.  What else is in RIP, and should not be seen via OSPF on R3 and R6.  Well, Lo101 and Lo103 for a start.  My first stab at solving this was:

router ospf 10 
  distance ospf external 130

Rethinking, that would cause a problem to the EIGRP 100 routes; they are external to OSPF too, and they should definitely be seen at R3 and R6 through OSPF.  So, abandon that idea.  I guess I am going to have to admit defeat and make an access list on each of R1, R3, and R6 to give RIP priority over OSPF for prefixes Lo101 and Lo103.  I hate using access-lists or prefix-lists to optimise routing.  It feels much too unscalable.  I prefer a generic solution.  But needs must, and this is a CCIE lab, not the real world.  

I can’t wait to try it all out.  No, I promised myself I would wait until tomorrow before I try anything.



  1. Do a good 400M of 4×100 IM all stroke work a good technique. That will keep the brain fresh!

    Comment by Doug — 05 Mar 2008 @ 11:03

  2. You are right that I should move to all-stroke, but I shall have to concentrate on getting the breathing right. At the moment I do 40 x 25m breast stroke, ‘cos it’s the easiest breathing rhythm – and a bit like a meditation. It always takes me a bit under 23 minutes, which is not so good, but it’s a faster than many in the pool, and not so bad for a 52-year-old. I do my best lab work in the pool!

    I should use a float for the freestyle, otherwise I put too much energy into the legs and I get out of breath. That kinda holds a lesson for the lab too.

    Comment by dorreke — 05 Mar 2008 @ 11:30

  3. Pulling for free style is a very good. Allows you to work the muscles with out the legs. For breathing issues, use a snorkel…

    I am not kidding, many competitors I swim with use this to work on stroke and not breathing. Great for doing 4x800s Free…
    Hey- I swim with many 40+ 60+ who are faster than me (I’m a sprinter).. I swim competitively here in the US (local competitions and national, no olympics :)…

    Yea the lab is driving me nuts. I’m out of swimming for a little while due to bad neck stiffness (too much studing).. I need a remedy… which does not include the computer.. (photography?).


    Comment by Doug — 05 Mar 2008 @ 12:19

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