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Home > Archive > CCNP > January 2003 > dotted decimal
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| wirelessboy 2003-01-07, 11:39 pm |
| dear all
how do we calculate osfp area in a dotted decimal format to a normal decimal number.
some confusion, different examples in jeff doyle have different formulas i feel
area 271= 0.0.1.15
area 16 = 0.0.0.16
area 3232243229 = 192.168.30.29
hey all you seniors please help!
regards | |
| peterd 2003-01-08, 4:38 am |
| hello,
calculate? I thought the area numbers were allocated by the 'techie' to fall in line with company policy (or his/her own idea of what it should be).
Can't we just give any old number that we want to as long as it makes sense within our network?
We can allocate decimal numbers, or dotted decimal, or a mixture of both, whatever we think is right. Or maybe I've misunderstood OSPF?
Regards
Peter | |
| wirelessboy 2003-01-08, 4:52 am |
| no dear peter
you are right, area ids can be anything, i just wanted to know how do we convert the dotted decimal format to a decimal format.
this is because, sometimes we give area0 as area 0.0.0.0 right?, similarly we have given areas as 192.168.10.X, and so on, i just wanted to find out the math involved as the CCIE book does not say much about it, and also the examples i had given before, all use different formulas .
regards | |
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| You have to convert the hex, into binary, split the binary up into chunks of 8 then convert each chunk into decimal.
I'll use 271 as an example:
271 Hex=100001111 or
00000001 00001111 Binary (N.B. chunks of 8)
1 . 15 or 0.0.1.15
Make sense?? | |
| wirelessboy 2003-01-09, 2:04 am |
| dear mat p
not quite clear because
area 16 = 0.0.0.16 as per jeff doyle
16 hex is 10110 binary, taking chunk of 8 we have 00010110=22, we should be getting area 16 = 0.0.0.22 | |
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| Sorry - I explained it wrong, I should have looked at the book without doing it off the top of my head!!
The numbers Jeff gives are in Decimal NOT hex like I stated, I even converted 271 correctly as if it was a decimal number!!
OK start again....
you understand that 0=0.0.0.0
you understand that 271=0.0.1.15, as per my last post(remember ignore the hex statement)
10 would be 0.0.0.10, remember each octet can only go up to 255 in decimal, therefore we only have to do the calculation I showed if the number is above 255.
Area 256 would be 0.0.1.0
and area 16 would be 0.0.0.16 - (I'll say again, ignore the fact that I mentioned Hex.)
So using the example he gives for area 3232243229 complete the following steps -
1. Convert to binary - no calculator allowed! ;-)
2. Split into Octets
3. Convert octets to decimal, and put a decimal point between each of them.
1. 3232243229= (for some reason it keeps wrapping the last two digits)
110000001010100000011110000111
01
2. 11000000 10101000 00011110 00011101
3. 192 168 30 29
= Area 192.168.30.29 | |
| wirelessboy 2003-01-09, 9:25 pm |
| yes mat, i think i got it complicated myself.
(for some reason it keeps wrapping the last two digits) = if u are saying this about the hex number, even i encountered it, but then i realised, what i learnt in school!
pentium=32 bit microprocessor, therefore max hex number = 8 digits
FFFFFFFF=4294967295=1(32 times), i hope i am right!
regards and thanks all |
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