On Wed, 2010-04-28 at 16:15 -0700, jack craig wrote: > When I learned about ip address, the network & host portions of the IP > and the netmask to differentiate the host & network numbers. I learned > a class A addr used a mask of 10.255.255.255. That number sequence is not correct. The old class A scheme could use addresses from 10.0.0.0 to 10.255.255.255, and the netmask for all of them being on the same subnet would be 255.0.0.0. > > eth0 Link encap:Ethernet HWaddr 00:26:18:FE:75:91 > inet addr:10.0.0.100 Bcast:11.255.255.255 Mask:254.0.0.0 Your broadcast and mask are odd, too. Try again... The netmask is an mask against where the boundary lay. For an addressing scheme like the 192.168.x.y scheme, the netmask could be 255.255.255.0 or 255.255.0.0. (it's usually the latter). The 255 portions go with the common portions of your addresses (everything that's the same on this side of your IP address is considered to be on the same subnet; and when an address is different, here, it's considered to be external, and you must go through the gateway to access it), and the zero portions of the netmask relate to the variable portions of your own internal IP addresses. The reason the third quad could be 255 or 0 is down to whether you're using all of the possible addresses in that scheme, or just some of them (i.e. where I've written "x" will be a fixed value), in a particular sub-network. For the 10.x.y.z private networking address scheme, you have three quads that you can use. And the same thing applies, if all of those addresses were on a common subnet, you'd probably use a netmask of 255.0.0.0, as that's the usual default mask for class A (all addresses start with 10, and all of the last three quads are available as internal addresses on the same subnet). But, if you were carving a big LAN up into separate networks, you might use a different mask. e.g. Building one might use 10.1.0.0 to 10.1.0.255 and building two might use 10.2.0.0 to 10.2.0.255, and you could use a netmask of 255.255.0.0 to keep them more isolated from each other. Or, more to the point, to make traffic go through a gateway so it could access the other subnet. On that note, the broadcast address will begin with the common prefix quads for that network (10.0... or 192.168...) and end with 255 as the last quad. So your broadcast address would be 10.0.0.255 not 11.255.255.255. If you're going to do some more unusual network addressing, you need to understand converting decimal to binary, and vice versa, or use an address & netmask calculator to work things out for you. -- [tim@localhost ~]$ uname -r 2.6.27.25-78.2.56.fc9.i686 Don't send private replies to my address, the mailbox is ignored. I read messages from the public lists. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
