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Unanswered Question
Nov 12th, 2013
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Hi all,

In the CCNA exam there was a question regarding EIGRP, I am not going to post specific details as I do not want to infringe the rules/copyright.

Suffice to say there are three routers and one I noticed was on a different subnet.

Therefore as part of the solution I went to change the IP address of an interface, however when doing so I got ^Invalid input detected at ^ marker' this referred to the 1 in the first octet of the address I had specified.

Can anyone explain why this is, this command is of course valid and specified at the correct place, It was also not possible to remove the IP address.

I have been thinking this over and I can not possibly understand why this happened, can anyone explain?

Sorry for the story but it is really bugging me and I cannot understand as to why this happened.



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Karthick Murugan Tue, 11/12/2013 - 09:13
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Hi Martin,

To my knowledge(I AM NOT 100% sure), in CCNA exams no real switches/routers will be used but just the simulator with limited command support. Probably, the solution that you attempted is not a valid solution and hence the configuration was not allowed.

Thanks & Regards,
Karthick Murugan

Martin Carr Tue, 11/12/2013 - 13:12
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Yes they are simulations, I was trying to reconfigure the address on an interface due to it not being on a common subnet with it's neighbors, thus adjacency would not form.

So surely it must be valid?


Richard Burts Tue, 11/12/2013 - 19:22
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I have seen symptoms similar to what you describe and at various times it was caused by one of these things:

- are you sure that you were in configuration mode on the correct interface

- are you sure that the 4 numbers of the address were separated by . (and not ,) and the same for the mask

- are you sure that you did not miss one of the . that separates the number in the address or in the mask.

- are you sure that in the mask  you did not have something like 225 or 252 or 522 and not 255

- are you sure that in the address (or in the mask) that none of the numbers was greater than 255

These are all simple mistakes and I wonder if one of them or something quite similar might have caused the issue that you encountered.



Martin Carr Wed, 11/13/2013 - 03:55
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Hi Rick,

Yes I was at the configuration for FA0/0 and I went to set the an address with a 240 mask. All the formatting was defiently correct (Not being funny but this is something I have done many a time) and I wasted a lot of time trying to figure out why it was not working, verifying I had not mistyped the commands.

The preset IP on the interface did indeed have a .252 mask, even so you should be able to reconfigure with an address in another subnet (like you can normally) it would not even let me remove the IP address.

I am thinking this may be a bug in the simulation and if so I will be taking this up with Pearson (From research I understand there was a bug in 2009 with a simulation) I just want reassurance I have not missed anything obvious before I do so.

The marker itself point at the 1 in the first octet, i.e. 192.




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