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Old 10-08-2004, 06:55 PM   #1
servnov
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what does /8 /32 etc. mean for IP?


I am confused as to what the /32 ending means on an IP address. I am assuming it is an IP address range, but would like to know for sure. Examples: 127.0.0.1/8 192.168.1.1/32
 
Old 10-08-2004, 07:15 PM   #2
maybbach
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theyre for the subnet mast. /8 is class A (255.0.0.0), /16 is class B (255.255.0.0), and class C is /24 (255.255.255.0). the number after the / is the number of bits used to make the number.
 
Old 10-08-2004, 07:22 PM   #3
scowles
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It's just another way of specifying the netmask. AKA: CIDR (Classless Inter-Domain Routing) Basically, it translates into the number of 1 bits set in the netmask. Each octet equals 8 bits. So...

127.0.0.1/8 = 127.0.0.1/255.0.0.0
192.168.8.2/32 = 192.168.8.2/255.255.255.255
192.168.8.0/23 = 192.168.8.0/255.255.254.0
 
Old 10-08-2004, 07:32 PM   #4
ranger_nemo
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It's masking.

To the computer, an IP is actually a set four groups or eight ones and zeros. So, in binary, 192.168.1.1 = 11000000.10101000.00000001.00000001

A mask is a similar series. Just count out the number after the / ...
/32 = 11111111.11111111.11111111.11111111
/24 = 11111111.11111111.11111111.00000000
/16 = 11111111.11111111.00000000.00000000
/8 = 11111111.00000000.00000000.00000000

Now, if you place the mask over the IP, any digit that is under a 1 cannot change, while a digit under a 0 can. So, an IP range of 192.168.1.1/24 will be anything from 192.168.1.0 to 192.168.1.255. Only the last group can change. An IP range of 192.168.1.1/16 will be anything from 192.168.0.0 to 192.168.255.255. It gets trickier if the mask is something like /13.
 
Old 10-09-2004, 01:14 AM   #5
RHELL
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Wow, looks like we've got this covered!
 
Old 10-09-2004, 09:13 AM   #6
servnov
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thanks. Do all loopbacks have 255.0.0.0 (/8) as subnet mask?
 
Old 10-09-2004, 09:30 AM   #7
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yeah, the whole of 127.*.*.* is for loopbacks
 
Old 10-10-2004, 01:16 AM   #8
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This is a great explanation. Thank you all!

--Shade
 
  


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