04-19-2010 07:11 AM - edited 03-06-2019 10:40 AM
Hi All
say I have been given a /27 network
say 10.100.1.0/27
How do I quickly work out how many /30's I can fit into the /27?
As its 3 bit places to the right, do I just do 2x2x2 which is 8 or is this wrong?
cheers
Carl
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04-19-2010 07:53 AM
carl_townshend wrote:
Hi All
say I have been given a /27 network
say 10.100.1.0/27
How do I quickly work out how many /30's I can fit into the /27?
As its 3 bit places to the right, do I just do 2x2x2 which is 8 or is this wrong?
cheers
Carl
Carl
8 is the correct answer.
I generally do it in my head like this
/27 = 255.255.255.224
/30 = 255.255.255.252 = 256 - 252 = 4 so /30 networks go up in 4
256 - 224 = 32 % 4 = 8
Another example - how many /29s are there in in a /25
25 = 255.255.255.128
/29 = 255.255.255.248 = 256 - 248 = 8 so /29 networks go up in 8.
256 - 128 = 128 % 8 = 16
Jon
04-19-2010 07:18 AM
Hi All
say I have been given a /27 network
say 10.100.1.0/27
How do I quickly work out how many /30's I can fit into the /27?
As its 3 bit places to the right, do I just do 2x2x2 which is 8 or is this wrong?
cheers
Carl
Hi Carl,
Check out the below links on subnetting hope that helps !!
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml
and one handy tool on subnetting also
http://www.cisco.com/cgi-bin/Support/IpSubnet/subnets.pl
Hope to Help !!
Ganesh.H
Remember to rate the helpful post
04-19-2010 07:53 AM
carl_townshend wrote:
Hi All
say I have been given a /27 network
say 10.100.1.0/27
How do I quickly work out how many /30's I can fit into the /27?
As its 3 bit places to the right, do I just do 2x2x2 which is 8 or is this wrong?
cheers
Carl
Carl
8 is the correct answer.
I generally do it in my head like this
/27 = 255.255.255.224
/30 = 255.255.255.252 = 256 - 252 = 4 so /30 networks go up in 4
256 - 224 = 32 % 4 = 8
Another example - how many /29s are there in in a /25
25 = 255.255.255.128
/29 = 255.255.255.248 = 256 - 248 = 8 so /29 networks go up in 8.
256 - 128 = 128 % 8 = 16
Jon
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