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New Member

eigrp routing

Hi all, If I have 2 sites both on a subnetted 10.x.x.x/24 network and I leave the auto summary command left on, will this not work as it thinks they both on the same network, will i need to use the no auto summarary command here ?

7 REPLIES
New Member

Re: eigrp routing

hello

use 'no auto-summary'.

depending on your topology you may get 2 10/8 routes on intermediary routers if you don't.

auto-summary is a remnant from dark ages of the internet, just used nowadays to test CCNA/CCNP candidates :)))

Etienne

Re: eigrp routing

I think auto summary pops up at all levels!

Paul,

Recently recertified.

Re: eigrp routing

What is in between them?

If they are both on 10.0.0.0 nets, but the link is 172.16.0.0 then you *will* get sumamrisation.

If the transit link is also in 10.0.0.0 then it will not summarise.

New Member

Re: eigrp routing

the link between them is a serial ppp link on 192.168.1.0/24

so nowadays is the no auto summarary always set ?

cheers

Carl

Re: eigrp routing

I am thinking this is suddenly looking very like an exam question, so I am NOT going to give an answer, but will instead flag a few of the important points.

The command reference for the appropriate version of IOS will tell you the defaults for various commands, but auto summary (if enabled) will happen here as we are moving between different major networks.

A few issues to ponder.

1. Ignoring EIGRP for a moment, if a router has a local route to, say, 10.1.2.0/24 and a route elswhere to 10.0.0.0/8 what will happen to a packet aimed at 10.1.3.27?

2. How does (no) IP CLASSLESS affect this?

3. When two EIGRP routers are both running a single LAN within 10.0.0.0/8 (eg 10.0.2.0/24 and 10.1.3.0/24) and autosummary is enabled, what routes will be in each router's tables.

Re: eigrp routing

Carl,

I have a suggestion, which you can take on board if you want, or you can ignore if you want. I don't mean any offence - I am suggesting this for your benefit.

You have been active on this forum for some years now, posting questions very regularly. It is evident from the type of questions that you post that you are using the forum as a training tool. That is well and good - so do I. But I wonder if you are getting the maximum benefit from the forum by just asking questions and reading the answers. After all, you could get most of that from the documentation.

I wonder whether you could improve your training by answering questions rather than asking them. If you discipline yourself, say, to answer at least one question for every one you ask, then I believe your training will become a lot more proactive. Don't be afraid of getting the answer wrong ... if you do get it wrong, there are plenty of well-meaning NetPros here who will put you back on the right track, and most of them are pretty nice about it too.

One other benefit you might experience is a few NetPro points. It is amazing how a few brownie points can improve your grasp of the material.

Good luck.

Kevin Dorrell

Luxembourg

Re: eigrp routing

Kevin makes some impotant points here. They are kind of why I suddenlt changed position earlier, but he out them so much better than I possibly could!

The greatest skill I have is not my knowledge of routing or switching, it is not knowing a little about MPLS. It is the inclination and ability togo find answers. Part of that is working outappropriate questions - eg earlier where I asked about what the connecting link was, as that is crucial when talking autosummary, and part of it is knowing how to go about finding answers. Neither of those are things I can easily say how I do - a little like a world class footballer struggling to explain how he knows where everyone else on the pitch is for example, but they are skills that can be developed - hopefully the three questions I asked of you in my later response will split the question down from one that may be a little daunting to small chunks you can easily find for yourself.

Even if you don't post responses, look at questions other people ask and see if you can find the answer and then compare what you find with what others come up with, and if you think you have the right answer, and someone disagrees, don't be afraid to challenge, but whenn you challenge something, try to explain why you think something is innacurate - that way leads to discussion, and that can trigger further relevant points that may illuminate why the disagreement has come about.

These forums were not about when I was studying for my CCIE. When doing that I spent a *LOT* of time in the lab, and quite often I would be sitting there with a rack of routers and switches wondering what to try. It was similar discussion groups that gave me things to learn and directly helped me learn more and pass the exams - not by simoly reading answers, but trying things, looking things up and getting the answers myself. An answer *you* have worked out will stick a whole lot better than an answer from people like Kevin, Jon, Edison or others, mainly because having worked it out, youprobably know not only that, for example, in a switched network switch six is the root bridge, but you know it is root because it has a lower priority, or a what the implcations of mac address are for root election.

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