Subnet Mask?

[mikeshn]

Can someone explain to me the purpose of subnet mask? And why subnet mask is alsways is 255.255.255.255?

Thanks

 

[minendo]

Originally posted by: mikeshn
Can someone explain to me the purpose of subnet mask? And why subnet mask is alsways is 255.255.255.255?

Thanks

Subnet mask is not always 255.255.255.255. I know that the first three sets have to do with a specified IP address. IP addresses are distributed by categories depending on the size of company or institution that uses them. I believe that an institution with the minimum range of IPs has the three different sets of numbers. I briefly heard about the way it works, but I am sure you can find more info.

 

[Journeyman]

Subnet masks aren't always 255.255.255.255 - in fact it usually WON'T be that.

The subnet mask basically tells the computer when it needs to look outside its particular router to find another machine...

A mask of 255.255.255.0 would mean that if the first three octets matched between a destination computer's IP address and yours, the machine is found within your subnet.

If that mask was 255.255.0.0, it would only look as far as necessary to search the last two octets.

So let's say my home network uses IP addresses in the form of 192.168.1.x, my computer is 192.168.1.66 and the computer downstairs is 192.168.1.65, with my subnet mask set to 255.255.255.0. If I try to contact the machine downstairs, my computer knows that it doesn't have to look outside of the 192.168.1.x range (inside my router) to find it.

Subnet masks are basically used to reduce network traffic...

 

[ScottMac]

Subnet masks identify which part of the address belongs to the network portion of the address, and which portion of the address is a host address.

If the network portion of the address is different, it's "Off-LAN," which signals the host to substitute the "Default Gateway" MAC address in the destination field of the frame.

FWIW

Scott