What does an IP ending in 0 signify?

When I tried to tell a norton firewall to allow traffic from the local network range, from thru, it said, "IP already allowed".

I looked on the "allowed List".  The firewall's "network wizard" had already allowed this:

What does this mean? I don't think I've seen an IP ending in 0 before (sorry). Does the "0" signify a range from "1 thru 254"?  

If so -- does that apply in any of the 4 octets?
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Guy Hengel [angelIII / a3]Billing EngineerCommented:
a 0 at the end is like a wild-card, allowing all ip addresses in that range 1-254

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angelIII is rite, adding to it

it is also called as network address

example (this address is for whole network staring from 192.168.1

in the same way for is the network address for

"The firewall's "network wizard" had already allowed this:"

this means that u'r firewall will allow all the address it the range to

A .0 address is meaningless without a corresponding subnet mask or CIDR notation - if your have a subnet wider than /24, an addressable host with an IP ending in .0 certainly exists.

That being said, I agree that the .0 address likely refers to the entire corresponding /24 subnet, since firewall manufacturers love to make their devices/software interpret the IP spec as creatively as possible, and their configuration interfaces are as brain-dead as possible...  

Regardless, it should be noted that the accepted answer is not correct for all cases.

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