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Moe Trin" <ibuprofin@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:slrnd8al52.i3t.ibuprofin@xxxxxxxxxxxxxxxxxxxx
> In article <gE9he.1405$sb5.1342@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Wolf wrote:
>
> Find RFC1878 at your favorite mirror.
>
> Old guy
You have not been doing your homework. Have you actually tried to get 253
netmask using "the bits?" You can't get there.
This should help: Take out a sheet of paper and start by creating 8
columns. This is going to be the 3rd octet. On the top line we write the
CIDR Prefix from left to right. Next we enter the bit place value.... Then
add the mask values..
/17 /18 /19 /20 /21 /22 /23
/24
128 64 32 16 8 4 2
1
128 192 224 240 248 252 254
255
Discontiguous networks are ugly and a sign you did not do your work right.
That can not be fixed with a netmask real or imaginary. It will require a
router and a protocol that understands classless routing-that leaves RIPv1
and IGRP off the list.
I have a really good book on the subject from a class I took last year:
"CCNP1: Advanced Routing." It goes into a lot of detail on the subjects of
VLSM, subnetting, supernetting, route summarization etc. The books for
CCNA1-4 cover it over and over, ad nauseum-and I recommend them also. The
actually way I calculate it takes another couple of lines. I had to be
able to do these by hand without using a calculator-in the 21st Century!
Today my phone has a subnet calculator.
Another Old Guy,
--
Wolf
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