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Cisco IOS Questions

Posted on 2004-03-24
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Last Modified: 2010-04-11
I have been out of working with Cisco for years.  I have a few questions from a basics standpoint.

1.  If you have saved a config (Copy run start), how do you kill that configuration?  Erase Start ?  I remember that you can erase the IOS completely and be back at a register config if you aren't careful.

2.  If you are dealing with a Back to Back serial config, say a 2514 and 2620, and the DCE side is on the 2514....  Let me just tell you what's happening and you tell me what you think.  --  I have a 2514 and a 2620 - When I configure the serial ports, I configure the clock at 1000000 on the 2514 and an IP of 192.168.5.2 /30 and on the other I have 192.168.5.3 /30 *forgive me if that's not exactly right.  Not positive about the IP's as I'm not in front of the router.  But the subnets are correct and they do ping* - But with that is my question.  The link seems to be flapping.  The interface goes UP and DOWN, UP and DOWN.  Over and over and over.

Any ideas?

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Question by:Hollmer
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pseudocyber earned 125 total points
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1. Answer:  write erase OR erase startup-config.  If you're in a switch, then it's delete nvram.

2.  Answer:  Quote:  "This is one I get asked a lot so here goes…

To enable back-to-back communication over the Serial
interfaces you have to perform a few tasks. These tasks
are fairly straight forward as soon as you fathom things
out.

The first thing to do is to ascertain which is the DTE
and which is the DCE interface. This can be done by
physically looking at the cable connector type. If you
are using X21 then the female connector is the DCE end.

The more professional way of achieving this is to issue
a show controller command. This command displays the
hardware (layer1) specifications including the cable
types connected.

Once you have found the DCE end you have to add the clock
rate to this interface. DCE devices provide the clock
rate and because you are emulating this you have to
manually get the router to provide the clocking source.

Router#conf t
Router(config)int s0
Router(config-if)clock rate 64000

The above commands would set the clock rate to roughly 64K.

Then set up a common network layer address such as
192.168.10.1 for the DCE and 192.168.10.2 for the DTE,
enable the interfaces and all being well you should have
the interface up and the line protocol up !!

That is all it takes to enable a back-to-back connection ! "

From: http://www.cramsession.com/articles/files/connecting-two-2500s---ci-182004-1504.asp
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by:Scotty_cisco
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Hollmer;

1: ) you just simply do router#write erase    then you reload the router.... The config will be gone the IOS will be intact.
2:) The router could be having a clocking issue... what Cables are you using cab-v.35-DTE and v.35 DCE ???  or do you have an internal CSU in the 2620 with an external on the 2514?   First thing check the cable connections and make sure your clock source is set to internal on the DCE side and the clock source is set to LINE on the DTE side.

Hope this helps

Scott
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by:Hollmer
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pseudocyber,

So you are SURE that this won't dump the IOS when you do a erase start ???

Thanks, Scotty for the assist.

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by:Hollmer
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If that's the case, how do you erase the IOS?  Because I know that I have screwed up in the past and done that.
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by:Scotty_cisco
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erase flash
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by:Hollmer
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How do I give you the assist, Scotty?  I appreciate your help.
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by:Scotty_cisco
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I have only ever posted 2 questions and only had 1 answered so ... I have no Idea LOL
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by:Hollmer
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Well thanks for your help anyway.  I really do appreciate it.
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