From: Li Guoyi (Guoyi.Li@scs.com.sg)
Date: Wed Jan 31 2007 - 06:17:03 ART
Thanks Scott & Loc,
I will try this, before the real lab...
________________________________
From: Loc Pham [mailto:ccie17030@yahoo.com]
Sent: Wed 1/31/2007 2:25 PM
To: Li Guoyi; swm@emanon.com; Filyurin, Yan; ccielab@groupstudy.com
Subject: RE: Multiple route redistribution points
Li,
Let me re-distribute (!!) what Scott and alot of us
doing along:
Set yourself up with 4-5-6 routers connect via
LAN/WAN.
1. Connect L1/L2. Now do something basic: router
Rip/OS (typ.) and monitor the routing table.
Now, do the redis from R-> OS, what do you see on
debug ip rout ?
Again, undo R->OS and do OS->R, what do you see ?
Now : perform R<->OS and again, do the deb ip
rout, what additional information show up @ route
table and debug ??
2. ....
You get the idea here: this is not something any of
us like to do in the ccie-lab, but you do need these
baby-step to learn and explore of A redist. into B
(transit ) into C .
BruceCaslow have a very complex and methological
step that you like to read up, check the GS archive
and the NMC site.
HTH,
lP
--- Li Guoyi <Guoyi.Li@scs.com.sg> wrote:
> Right. In most cases, we don't need to adjust AD. I
> feel router is smart
> enough to do the redistribution correctly. Do you
> have some good
> examples on the scenarios where multiple
> redistribution points cause
> routing loops? Like between EIGRP and OSPF, or OSPF
> and BGP
>
> Another thing is, let us say, the routing loop does
> happen after the
> redistribution at multiple points , it may take long
> time (I am not sure
> how long, maybe a few minutes) to be detected. The
> symbol may be routes
> come and go, and come and go,etc . In this case, by
> checking the routing
> table, we may have wrong impression that
> redistribution is working fine,
> as the routes are there. So how can we ensure the
> redistribution is ok?
>
> Is there a systematic approach to do redistribution
> in the lab?
>
> -----Original Message-----
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Wednesday, January 31, 2007 10:00 AM
> To: Li Guoyi; 'Filyurin, Yan';
> ccielab@groupstudy.com
> Subject: RE: Multiple route redistribution points
>
> During practice, you take the extra steps... Until
> you can anticipate
> what's going to happen. (think like the router
> does)
>
> As for mutual redistribution on the same router, it
> often poses no
> problem.
> Most protocols (other than RIP) notice the
> difference of internal vs.
> external routes. Other times, the AD may already be
> in the direction
> you want it to be, so nothing needs to be done.
>
> Don't count on this though! Especially in the lab.
> Things are seem TOO
> EASY are often areas where points are lost!
>
> But watching what happens to your routing table(s)
> is really the way to
> go.
> Even in the lab, doing "debug ip routing" isn't a
> bad thing as long as
> you are used to seeing the output and therefore know
> what it is you are
> looking at!
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service
> Provider) #4713,
> JNCIE #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPexpert VP - Curriculum Development
> IPexpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Li Guoyi
> Sent: Tuesday, January 30, 2007 8:11 PM
> To: Scott Morris; Filyurin, Yan;
> ccielab@groupstudy.com
> Subject: RE: Multiple route redistribution points
>
> Hi Scott,
>
> I am a bit confused by mutual redistribution also.
> Are there any rules for multiple route
> redistribution points? Is it
> always necessary to adjust AD? In the workbook
> solutions, sometimes no
> loop prevention measures (like ajusting AD) are
> taken at all. How do we
> know when the prevention measures are necessary? In
> addition, there are
> many combinations of mutual redistribution, like Rip
> and OSPF, OSPF and
> Eigrp, OSPF and BGP, etc. Will the rules apply to
> all the combinations?
>
> Or as you said, we need to perform the step by step
> redistribution
> during lab exam? It will take long time to finish
> redistrition portion
> this way.
> Please advise.
>
> Thanks,
> Li
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Scott Morris
> Sent: Tuesday, January 30, 2007 3:48 AM
> To: 'Filyurin, Yan'; ccielab@groupstudy.com
> Subject: RE: Multiple route redistribution points
>
> As opposed to their being a "best way" (which there
> rarely is anything
> that fits all circumstances), the best thing you can
> do is sit and plan,
> configure and watch what occurs at each point.
>
> A good way with this involves both TCL script for
> pinging (every IP
> address of your network should be listed) and
> debugs...
>
> Before doing any redistribution it is simple to
> predict what things you
> can or cannot ping from any one location. Before
> doing any
> redistribution, enable "debug ip routing". Assuming
> you have stable
> protocols to begin with, when you do your first
> redistribution, you
> should see a predictable influx of routes and be
> able to know what
> things can or cannot be pinged from any location.
> (gaps here may answer
> your redistribute connected
> question)
>
> As you add more and more redistribution points, each
> time, repeat the
> process. Again, you'll be able to watch the routes
> move (from the
> debug) and test things with pings to make sure what
> you are getting
> lines up with what you thought should be happening.
>
> This process, while very tedious, is the best way to
> get a true grasp
> about what your router is (or is not) thinking
> during the redistribution
> processes. The ability to think it through and
> predict what will happen
> will help you figure out what will happen in any
> situation that you
> happen to run across. Also, using route tags may be
> a more efficient
> way of allowing/not allowing routes in different
> places.
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service
> Provider) #4713,
> JNCIE #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPexpert VP - Curriculum Development
> IPexpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Filyurin, Yan
> Sent: Monday, January 29, 2007 2:03 PM
> To: ccielab@groupstudy.com
> Subject: Multiple route redistribution points
>
> Hello Group Study. I have a possible set of
> questions regarding route
> redistribution. Let's say I have 4 routers A, B, C
> and D, all
> interconnected and running the same routing
> protocol. For example OSPF.
> Routers A and B connect to the same RIP domain and
> routers C and D
> connect to say EIGRP domain. Mutual redistribution
> needs to be done
> between all IGP protocols.
>
> The first task that needs to be done is that since
> there are multiple
> redistribution points, all I have to do is through
> the use of route tags
> control so that routes from one routing protocol
> don't redistributed
>
=== message truncated ===
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