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27
votes
6answers
21k views

CIDR for Dummies

I understand what CIDR is, and what it is used for, but I still can't figure out how to calculate it in my head. Can someone give a "for dummies" type explanation with examples?
21
votes
4answers
13k views

Reverse DNS in a CIDR world

Reverse DNS seems to be strongly tied to class boundaries, what methods exist now that CIDR is the standard to delegate authority for a subnet? If multiple methods exist which one is best? Do you ...
7
votes
4answers
2k views

CIDR Ranges for Everything except RFC1918

I'm looking for a list of CIDR blocks for "The Internet", i.e. everything from 0.0.0.0 to 223.255.255.255, excluding RFC1918 address space of 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 (yes, I know ...
4
votes
1answer
175 views

Is it safe to assume that two hosts on the same /24 network belong to the same AS-number?

Assume two IP-addresses in the same /24 network (say 1.2.3.*): 1.2.3.X 1.2.3.Y Is it safe to assume that these two hosts belong to the same AS-number? If not, roughly how often is that the case ...