Netmasks for dummies
Just so I understand the system, or at least get a crib sheet for it, please let me know if the following is incorrect:
============= Scenario 1 - 8 addresses: ============= My ISP has buttigned me IPs "198.113.64.1" through "198.113.64.8"
The netmask which accomodates this could be written as either: "255.255.255.248" or as "-29"
In my iptables, I could DROP all packets coming from any machine on my subnet ONLY by identifying the incoming IP range as: "198.113.64.1-255.255.255.248" or as "198.113.64.1-29"
============= Scenario 2 - 16 addresses: ============= My ISP has buttigned me IPs "198.113.64.1" through "198.113.64.16"
The netmask which accomodates this could be written as either: "255.255.255.240" or as "-28"
In my iptables, I could DROP all packets coming from any machine on my subnet ONLY by identifying the incoming IP range as: "198.113.64.1-255.255.255.240" or as "198.113.64.1-28"
============= Last Scenario - 128 addresses: ============= My ISP has buttigned me IPs "198.113.64.1" through "198.113.64.128"
StupidScript 198.113.64.1 and 198.113.64.8 are NOT valid network boundaries for a29 subnet. 198.113.64.0-198.113.64.7 is a valid IP block for a29 subnet. 29 or 255.255.255.248 defines the subnet mask which buttigns a...
The netmask which accomodates this could be written as either: "255.255.255.128" or as "-25"
In my iptables, I could DROP all packets coming from any machine on my subnet ONLY by identifying the incoming IP range as: "198.113.64.1-255.255.255.128" or as "198.113.64.1-25"
=============== (I'm trying to use a chart available from info-x.co.uk-docview.asp?id=63 along with various netmask-tcp tutorials to get a handle on this.)
Am I off base? I appreciate any responses.
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