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Can someone explain about IP's
Hi.
This is a newbie question but I'm always confused about when people talk about IP's like /24 /27
I'm looking at https://www.ovh.com/us/dedicated-servers/free-ips.xml right now and it says 256 ips is /24
What is the correlation between those two numbers, or the relation between 128 and /25.
In a conversation when someone writes /25 how am I supposed to know it means 128 ips.
Can someone please explain that.
Comments
https://en.wikipedia.org/wiki/IPv4_subnetting_reference
2n - 2
"n" is the number of zeros in the subnet mask
(upper "n")
This may be a bit clearer, look down at the chart. But have a read, it's easy enough to understand.
http://www.ripe.net/internet-coordination/press-centre/understanding-ip-addressing
/x means 2^(32-x) IPs
ovh is slightly different, you can have full use of the block, say /29 there'll be 8 IPv4s available when used with a ds. for other /29 blocks, you'll get to use only 5 IPv4 with a ds.
Depends how you're using the IPs. If you add the first IP of a /29 to a bridge interface, as an example you can use 5 IPs vor VMs and the first one is the gateway.
If you use routed mode for your VMs (example OpenVZ), you can use 8x /32 -> All IPs from the /29. But only if it's routed to your server.
ipv4 addresses are 32 bits. The number after the slash tells you how many ones there in the address counting from the left. So /24 = 24 ones. 32-24 = 8. So you have 8 binary digits that you can use to represent your subnet and 2 to the power 8 is 256. 2 of the IPs will likely be used for the gateway and broadcast address so that leaves 254 usable IPs.