RE: Routing loops

From: Joseph Brunner (joe@affirmedsystems.com)
Date: Mon Sep 17 2007 - 17:55:21 ART

Actually we don't need to change AD unless we are going to force natural
selection of route path towards a routing protocol which would not normally
be the better ad. I.E. prefer EIGRP EX over OSPF/RIP, etc.

If you just want prevent route feedback, you can just tag going between
protocols, carry that tag back around to the other router and deny
redistribution for routes being redistributed that carry that same tag. This
ensures we don't "feedback" routes into a protocol where they were
originally learned.

So assume we are redistributing between EIGRP AS 10 and OSPF on two routers.

So the configuration of redistribution under the OSPF process looks like
this...

router ospf 1
redistribute eigrp 10 subnets route-map EIGRP->OSPF

And the route-map...

route-map EIGRP->OSPF deny 5
satch tag 500

And ends with permitting all else, and sets the tag for the other router to
Catch on its identical "deny 5" sequence

route-map EIGRP->OSPF permit 10
set tag 500

Now on Eigrp's redistribution command we do the same thing...

router eigrp 10
redistribute ospf 1 route-map OSPF->EIGRP metric 1500 10 255 1 1500

route-map OSPF->EIGRP deny 5
match tag 500

And ends with permitting all else, and sets the tag for the other router to
Catch on its identical "deny 5" sequence

route-map OSPF->EIGRP permit 10
set tag 500

-Joe

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Rich
Collins
Sent: Monday, September 17, 2007 3:37 PM
To: Keith Bizzell
Cc: Cecil Wilson; ccielab@groupstudy.com
Subject: Re: Routing loops

Routing redistribution is a big topic and I have numerous questions
myself. I have jotted down some notes but can't say that I understand it
all yet.

For example on RIP<>OSPF I see this suggested :

   - *RIP --> OSPF:* Use administrative distance on the RIP side for the
      RIP networks to lower the distance to less than OSPF
      - *RIP <-- OSPF:* OK: OSPF = 110 , RIP = 120

I have seen examples where this is used even if there is only ONE router
doing the mutual redistribution. Why is it necessary in such an example?

On 9/17/07, Keith Bizzell <mkbcoolman@gmail.com> wrote:
>
> As a friend of mine always says, 'Pretend you're a packet'.
>
> You should be able to spot routing loops pretty quickly with a tcl script
> and traceroute. If my script doesn't work, I'll trace down the route to
> find out where the loop is. Usually, you see routing loops where you have
> two routers both participating in two route processes with redistribution
> (
> i.e. mutual redistribution between rip/ospf). In those cases, it's good
> to
> use tagging or manipulate the distance within the lab requirements.
>
> If you have a good workbook, you should get beat to death with routing
> loops. That's a good thing, since it's impossible to pass the lab if you
> have a routing loop. Eventually, you'll get to a point where you just
> look
> at the diagram and immediately see all the possible routing loops.
>
>
>
> On 9/17/07, Cecil Wilson <Cecil.Wilson@flextronics.com> wrote:
> >
> > Hello GS
> > What is the best way to spot or identify routing loops? Is there
> > something that can readily ID routing loops? What are some of the
> > things that could cause routing loops
> > All inputs, links comments are welcome
> >
> > Thanks for all inputs
> >
> >
> > Cecil G. Wilson
> > IT Network Services
> > Office: (901) 215-2710
> > Cell: (901) 601-6201
> > cecil.wilson@flextronics.com
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Scott Morris
> > Sent: Sunday, September 16, 2007 12:19 AM
> > To: 'Narbik Kocharians'
> > Cc: 'Brian Dennis'; 'Gary Duncanson'; 'Neil Moore';
> > ccielab@groupstudy.com
> > Subject: RE: My CCIE jurney
> >
> > Not by what I'd seen of the lower certs for DC. *shrug* Security,
> > lotta switching, storage. But I didn't see voice listed, or at least
> > wasn't paying that much attention.
> >
> > Dunno.
> >
> > Scott
> >
> > _____
> >
> > From: Narbik Kocharians [mailto:narbikk@gmail.com]
> > Sent: Saturday, September 15, 2007 10:01 PM
> > To: swm@emanon.com
> > Cc: Brian Dennis; Gary Duncanson; Neil Moore; ccielab@groupstudy.com
> > Subject: Re: My CCIE jurney
> >
> >
> > Storage is different from data center, i thought data center was combo
> > of Voice, R&S, security and storage.
> >
> >
> > On 9/15/07, Scott Morris <swm@emanon.com> wrote:
> >
> > That would be Storage 2.0....
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Narbik Kocharians
> > Sent: Saturday, September 15, 2007 9:17 PM
> > To: Brian Dennis
> > Cc: Gary Duncanson; Neil Moore; ccielab@groupstudy.com
> > Subject: Re: My CCIE jurney
> >
> > I totally agree how about data center?
> >
> > On 9/15/07, Brian Dennis < <mailto:bdennis@internetworkexpert.com>
> > bdennis@internetworkexpert.com> wrote:
> > >
> > > The next track appears to be wireless.
> > >
> > > Brian Dennis, CCIE4 #2210 (R&S/ISP-Dial/Security/SP)
> > > bdennis@internetworkexpert.com
> > >
> > > Internetwork Expert, Inc.
> > > http://www.InternetworkExpert.com
> > > Toll Free: 877-224-8987
> > > Direct: 775-745-6404 (Outside the US and Canada)
> > >
> > >
> > > >----- Original Message -----
> > > Subject: Re: My CCIE jurney
> > > Date: Sat, September 15, 2007 16:19
> > > From: "Gary Duncanson" < <mailto:gary.duncanson@googlemail.com>
> > gary.duncanson@googlemail.com>
> > >
> > > > Thank you Neil,
> > > >
> > > > Well that's good to know regarding my plans. Have you any ideas on
> > > > any
> > > new
> > > > tracks we might see in CCIE in future?
> > > >
> > > > Rgds
> > > > Gary
> > > > ----- Original Message -----
> > > > From: "Neil Moore" <neil@droopy.com>
> > > > To: "Gary Duncanson" < gary.duncanson@googlemail.com>
> > > > Cc: <ccielab@groupstudy.com>
> > > > Sent: Sunday, September 16, 2007 12:09 AM
> > > > Subject: Re: My CCIE jurney
> > > >
> > > >
> > > > >I do not see it personally. There are different tracks with
> > > > >different goals to master in that technology.
> > > > >
> > > > > Neil Moore CCIE5 #10044 (R/S,Security,SP,Voice,Storage)
> > > > >
> > > > > Gary Duncanson wrote:
> > > > >> Hi Neil,
> > > > >>
> > > > >> I realise you have no crystal ball but will all these CCIE tracks
> >
> > > > >> get 'smushed' together at some point or will we see even more
> > > designations in
> > > > >> future do you think?
> > > > >>
> > > > >>
> > > > >> ----- Original Message ----- From: "Neil Moore" <
> > neil@droopy.com>
> > > > >> To: "Scott Vermillion" <scott_ccie_list.com@it-ag.com>
> > > > >> Cc: "'Narbik Kocharians'" < narbikk@gmail.com>; "'Scott Morris'"
> > > > >> <smorris@ipexpert.com>; "'Guyler, Rik'" <
> > rguyler@shp-dayton.org>;
> > > "'darth
> > > > >> router'" <darklordrouter@gmail.com>; < ccielab@groupstudy.com>
> > > > >> Sent: Saturday, September 15, 2007 11:19 PM
> > > > >> Subject: Re: My CCIE jurney
> > > > >>
> > > > >>
> > > > >>> For me it was just to get a complete set... when I started it
> > > > >>> was
> > > just
> > > > >>> R&amp;S,Security and C/S(Now Service Provider) then another came
> >
> > > > >>> along..
> > > > >>> then another came along..
> > > > >>>
> > > > >>> Neil Moore CCIE5 #10044 (R/S,Security,SP,Voice,Storage)
> > > > >>>
> > > > >>> then this CCDE came along ...
> > > > >>>
> > > > >>>
> > > > >>> Scott Vermillion wrote:
> > > > >>>>> If you are over 70 and still saying things like that publicly,
> >
> > > > >>>>> then you just bought some of those blue pills
> > > > >>>> and
> > > > >>>>> you think it works for everything
> > > > >>>>
> > > > >>>>
> > > > >>>> FOTFLMAO!! Now *that* was funny!
> > > > >>>>
> > > > >>>>
> > > > >>>> (come to think of it, anybody know a good, discrete source for
> > > little
> > > > >>>> blue
> > > > >>>> pills?) ;~)
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>> -----Original Message-----
> > > > >>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > > Behalf Of
> > > > >>>> Narbik Kocharians
> > > > >>>> Sent: Saturday, September 15, 2007 11:45 AM
> > > > >>>> To: Scott Morris
> > > > >>>> Cc: Guyler, Rik; darth router; ccielab@groupstudy.com
> > > > >>>> Subject: Re: My CCIE jurney
> > > > >>>>
> > > > >>>> I got my first two in 20 days and the third after 12 months,
> > > > >>>> so it
> > > was
> > > > >>>> a
> > > > >>>> total of 3 in 13 months but to get 4??????, who knows, it all
> > > depends
> > > > >>>> on
> > > > >>>> what you are doing and how comfortable you are with the stuff.
> > > > >>>> When
> > > i
> > > > >>>> took
> > > > >>>> security CCIE, the only security appliance in the lab was a
> > PIX.
> > > But
> > > > >>>> nowadays the track has 2 ASAs, one PIX, one VPN and a 42xx box
> > > > >>>> plus
> > > 9
> > > > >>>> routers and 2 switches, with may be 1 percent of routing &amp;
> > > Switching
> > > > >>>> stuff
> > > > >>>> (If that). When i took my security, routing and switching was a
> >
> > > > >>>> big part of the lab, what i am trying to say is that there was
> > > > >>>> lots of
> > > overlapping
> > > > >>>> stuff
> > > > >>>> between the three tracks.
> > > > >>>>
> > > > >>>> Good luck mate, if you can do it, go for it. I will definitely
> > > > >>>> congratulate you. Based on what you wrote, it shows lots of
> > > > >>>> confidence.
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>> You are either under 20 or over 70 years of age. If you are
> > > > >>>> under
> > > 20,
> > > > >>>> then I
> > > > >>>> can see where you are coming from. If you are over 70 and still
> > > saying
> > > > >>>> things like that publicly, then you just bought some of those
> > > > >>>> blue pills and you think it works for everything (just kidding)
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>> On 9/15/07, Scott Morris < smorris@ipexpert.com> wrote:
> > > > >>>>> In my case, it was an evolution. If you had asked my back
> > > > >>>>> when studying for my R&amp;S if I would plan on getting more
> > > > >>>>> than one, my response
> > > would
> > > > >>>>> have
> > > > >>>>> been
> > > > >>>>> "Are you f#*$&amp;ing insane?" :)
> > > > >>>>>
> > > > >>>>> But as I progressed working in different technology areas, and
> > > doing
> > > > >>>>> the
> > > > >>>>> recert exams (also qualifying exams) it was kind of natural to
> >
> > > play
> > > > >>>>> around
> > > > >>>>> with it.
> > > > >>>>>
> > > > >>>>>
> > > > >>>>> Scott Morris, CCIE4 (R&amp;S/ISP-Dial/Security/Service
> > > > >>>>> Provider)
> > > #4713,
> > > > >>>>> JNCIE
> > > > >>>>> #153, CISSP, et al.
> > > > >>>>> CCSI/JNCI-M/JNCI-J
> > > > >>>>> VP - Technical Training - IPexpert, Inc.
> > > > >>>>> IPexpert Sr. Technical Instructor
> > > > >>>>>
> > > > >>>>> A Cisco Learning Partner - We Accept Learning Credits!
> > > > >>>>>
> > > > >>>>> smorris@ipexpert.com
> > > > >>>>>
> > > > >>>>> Telephone: +1.810.326.1444
> > > > >>>>> Fax: +1.810.454.0130
> > > > >>>>> http://www.ipexpert.com
> > > > >>>>>
> > > > >>>>>
> > > > >>>>> -----Original Message-----
> > > > >>>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > > Behalf
> > > > >>>>> Of
> > > > >>>>> Guyler, Rik
> > > > >>>>> Sent: Saturday, September 15, 2007 10:44 AM
> > > > >>>>> To: 'darth router'; ccielab@groupstudy.com
> > > > >>>>> Subject: RE: My CCIE jurney
> > > > >>>>>
> > > > >>>>> Roman has 5 titles to his name but you're right dude...it's
> > > > >>>>> insane
> > > to
> > > > >>>>> even
> > > > >>>>> plan it and lay it out. I wonder if Scott, Brian, Narbik et
> > > > >>>>> al
> > > really
> > > > >>>>> planned to get multiple titles or it just kinda evolved that
> > way?
> > > > >>>>>
> > > > >>>>> Rik
> > > > >>>>>
> > > > >>>>> -----Original Message-----
> > > > >>>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com
> > <mailto:nobody@groupstudy.com> ] On
> > > Behalf
> > > > >>>>> Of
> > > > >>>>> darth router
> > > > >>>>> Sent: Saturday, September 15, 2007 9:55 AM
> > > > >>>>> To: Ian Blaney
> > > > >>>>> Cc: midvangur41@simnet.is; ccielab@groupstudy.com
> > > > >>>>> Subject: Re: My CCIE jurney
> > > > >>>>>
> > > > >>>>> Dang man,
> > > > >>>>>
> > > > >>>>> pass the crack pipe my way. I think you are definitely telling
> >
> > > > >>>>> a
> > > joke
> > > > >>>>> to
> > > > >>>>> get
> > > > >>>>> responses. I do not think that is even possible. Maybe if you
> > > > >>>>> are
> > > an
> > > > >>>>> industry expert in all of those areas already, which is also a
> >
> > > > >>>>> bit improbable. You certainly could not have a day job and do
> > > > >>>>> all
> > > that.
> > > > >>>>> Anyone can brain dump the written exams.
> > > > >>>>>
> > > > >>>>> DR
> > > > >>>>>
> > > > >>>>> On 9/15/07, Ian Blaney < ian.blaney@gmail.com> wrote:
> > > > >>>>>> Jon
> > > > >>>>>>
> > > > >>>>>> All I can say is good luck but trying not to discourage your
> > > > >>>>>> enthusiasm you may fall to earth with a large BUMP!!!!
> > > > >>>>>>
> > > > >>>>>> Concentrate on one lab at a time. See how you get on with the
> >
> > > R&amp;S and
> > > > >>>>>> take it from there.
> > > > >>>>>>
> > > > >>>>>> Ian
> > > > >>>>>>
> > > > >>>>>> On 9/15/07, midvangur41@simnet.is <midvangur41@simnet.is>
> > wrote:
> > > > >>>>>>> Hello all
> > > > >>>>>>>
> > > > >>>>>>> I am new to this list. I have been studying for the CCIE R%S
> >
> > > > >>>>>>> and Voice
> > > > >>>>>> for
> > > > >>>>>>> the last 12 months and I am taking my 1. attempt for the
> > > > >>>>>>> CCIE
> > > lab
> > > > >>>>>>> R&amp;S
> > > > >>>>>> the 9.
> > > > >>>>>>> of november. I feel good about my first atempt. I am
> > > > >>>>>>> confident
> > > about
> > > > >>>>>>> internal protocols and layer 2 but I must practice Bgp and
> > > > >>>>> multicasting.
> > > > >>>>>> I
> > > > >>>>>>> have taken the following aproach to the CCIE:
> > > > >>>>>>> From 2000 I have been studying for the CCIE R&amp;S. On the
> > > > >>>>>>> way
> > > I have
> > > > >>>>>>> taken few small Cisco exams and I have consentrated my work
> > > towards
> > > > >>>>>>> the
> > > > >>>>> exam.
> > > > >>>>>> This
> > > > >>>>>>> year I have taken 4 CCIE writtens R&amp;S, Voice, Service
> > > Provider and
> > > > >>>>>> Storage.
> > > > >>>>>>> I am consentrating on taking all 4 next 2 years. After that
> > > > >>>>>>> I
> > > will
> > > > >>>>>>> take
> > > > >>>>>> CCIE
> > > > >>>>>>> security as my last CCIE. Here is my scedule:
> > > > >>>>>>> 9. nov 2007 CCIE R&amp;S
> > > > >>>>>>> Mars 2008 CCIE SP
> > > > >>>>>>> Aug 2008 CCIE Voice
> > > > >>>>>>> Des 2008 CCIE Storage
> > > > >>>>>>> May 2009 CCIE Security
> > > > >>>>>>>
> > > > >>>>>>> Everything is possible
> > > > >>>>>>> Regards
> > > > >>>>>>> Jon
> > > > >>>>>>>
> > > > >>>>>>>
> > > ____________________________________________________________________
> > > > >>>>>>> ___ Subscription information may be found at:
> > > > >>>>>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>>>
> > > ______________________________________________________________________
> >
> > > > >>>>>> _ Subscription information may be found at:
> > > > >>>>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>>
> > > ______________________________________________________________________
> > > _
> > > > >>>>> Subscription information may be found at:
> > > > >>>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>>
> > > > >>>>>
> > > ______________________________________________________________________
> >
> > > _
> > > > >>>>> Subscription information may be found at:
> > > > >>>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>>
> > > > >>>>>
> > > ______________________________________________________________________
> > > _
> > > > >>>>> Subscription information may be found at:
> > > > >>>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>>
> > > > >>>>
> > > > >>>>
> > > > >>>>
> > > > >>>> --
> > > > >>>> Narbik Kocharians
> > > > >>>> CCIE# 12410 (R&amp;S, SP, Security) CCSI# 30832
> > > > >>>> www.Net-WorkBooks.com
> > > > >>>>
> > > > >>>>
> > > ______________________________________________________________________
> > > _
> > > > >>>> Subscription information may be found at:
> > > > >>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>>
> > > > >>>>
> > > ______________________________________________________________________
> >
> > > _
> > > > >>>> Subscription information may be found at:
> > > > >>>> http://www.groupstudy.com/list/CCIELab.html
> > > > >>>
> > > > >>>
> > > ______________________________________________________________________
> > > _
> > > > >>> Subscription information may be found at:
> > > > >>> http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > > ____________________________________________________________________
> > > > ___ Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > >
> > > ______________________________________________________________________
> > > _ Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
> > >
> >
> >
> >
> > --
> > Narbik Kocharians
> > CCIE# 12410 (R&S, SP, Security)
> > CCSI# 30832
> > www.Net-WorkBooks.com
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
> >
> >
> >
> >
> >
> > --
> > Narbik Kocharians
> > CCIE# 12410 (R&S, SP, Security)
> > CCSI# 30832
> > www.Net-WorkBooks.com
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
> > Legal Disclaimer:
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>
>
>
> --
> Keith Bizzell
> CCIE # 18798
>
> _______________________________________________________________________
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