CIDR or VSLM

Jason Jones 22 years ago

Hey all. Im about to take my 640-607 exam. however im having a problem understanding subnetting. My main problem is that i dont understand the difference between a CIDR and VSLM. Where i work, we do our subnetting totally diffent that what all the Cisco study material teaches. For example: at Bellsouth.net

68.157.156.6/29 would equal=
68.157.156.6= Network Address (on ISP end)
68.157.156.7= Router Address
68.157.156.8 - .12= host address
68.157.156.13= broadcast address.

Then on top of that, we put the Router address on the LAN side of the router and customer has to turn NAT off. The WAN side of the router is doing PPPoE and actually pulls a dynamic ip address (which we tell the customer to just ignore!) From there, the ip addresses are accessable (pingable) from the internet. I actually understand this but i think i need to clear this out of my head before i take the test. I keep getting the questions wrong on ever practice test i take.

THANKS IN ADVANCE FOR ANY HELP, SUGGESTIONS, or ADVICE

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futura 19 years ago

Hi,

I have read the above but it does not really answer my question.

I am studying for CCNA and the material covers route summarisation and CIDR.

I am having issues spotting the differences between the two, they are treated seperatly under two different chapters and to me both seem to perform the exact same function, which is to summarise a range subnets addresses into one single subnet address.

If someone can explain the main differences that would be good!

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q_q_anonymous 19 years ago

CIDR block is *given to you*. CIDR notation is slash notation.

VLSM is something *you do* to subnet the CIDR block

Route summarization is something you do to summarize your routes(or subnets i guess).

Supernetting is similar to route summarization. I think it is when the routes/subnets you are summarizing are on the same interface.

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