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I ahve created aws VPC and try to create additional CIDR. I have always got overlaps error whever values I tried /8, /0, /16, /32:

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What are correct values?

Cherry
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  • When downvote add a comment please. I have seen example with same CIDR values on VPC and do not understand why I get error here – Cherry Nov 06 '19 at 14:17
  • Every CIDR block with a mask 10.0.0.0, regardless of block size, is going to overlap, by definition. 10.1.0.0/16, for example, would not overlap with 10.0.0.0/16. – Adrian Nov 06 '19 at 14:17
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    Do you actually need to add an additional range of IP addresses? You have a 10/16 which is 65,536 IP addresses (minus 5 for VPC usage). If you do, go to 10.1.0.0/16 then 10.2.0.0/16. Or add other RFC1918 ranges such as subsets of 172.16/16 or 192.168/16. You really need to understand RFC1918 and what /16, /24 etc. relate to. – jarmod Nov 06 '19 at 14:28

1 Answers1

10

10.0.0.0/16 covers 10.0.0.0 through 10.0.255.255 (ie /16 means the first 16 bits are constant, the rest vary through the whole remaining range) so 10.1.0.0/16, 10.2.0.0/16, 10.3.0.0/16 ... 10.255.0.0/16 do not overlap.

Tony BenBrahim
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    A concept that no one else in my searches seem to be able to answer simply and succinctly. Thank you! – badfun Apr 28 '22 at 15:41