Subnet Mask question

11111111 11111111 11111111 00000000 is your /24
11111111 11111111 11111110 00000000 is your /23
11111111 11111111 11111100 00000000 is your /22 and 255.255.252.0 is the subnet you'll need to support 192.168.0.0 - 192.168.2.255

Here's a subnet mask table for reference: http://www.bgp4.as/netmask.txt

Here's another good calculation tool for you...http://library.mobrien.com/net.shtml

Yet another good link on subnetting...http://www.cisco.com/warp/public/701/8.html :)

You asked:

> 192.168.0.0 - 192.168.0.255 has a subnet mask of 255.255.255.0 and so is /24

yes

> 192.168.0.0 - 192.168.1.255 has a subnet mask of 255.255.254.0 and so is /23

yes

> 192.168.0.0 - 192.168.2.255 has a subnet mask of 255.255.253.0 and so is ????

That is neither a subnet nor is 255.255.253.0 a valid subnet mask [unless non-contiguous subnet masking is allowed, but that's way, way out there].

If you are assigned 192.168.0.0 - 192.168.2.255 by a provider, it means that they will route those addresses to you, and you can use them as you choose.  You can't represent that "directly" in CIDR notation, but what it "probably" means is that they are going to route 192.168.0.0/23 and 192.168.2.0/24 to you.  What you do with those addresses and how you actually subnet them on your end is up to you, but you can NOT summarize them as "one" route unless you have also been assigned 192.168.3.255, in which case you would have 192.168.0.0/22.

Thanks guys

sirbounty;

>11111111 11111111 11111111 00000000 is your /24
>11111111 11111111 11111110 00000000 is your /23
>11111111 11111111 11111100 00000000 is your /22 and 255.255.252.0 is the subnet you'll need to support >192.168.0.0 - 192.168.2.255

But doesn't /22 refer to 192.168.0.0 - 192.168.3.255?

I was wondering if there was a way to represent irregular (or non-contigious if you like) subnet masks?

jeffkell;

>That is neither a subnet nor is 255.255.253.0 a valid subnet mask [unless non-contiguous subnet masking is allowed, >but that's way, way out there].
>
>If you are assigned 192.168.0.0 - 192.168.2.255 by a provider, it means that they will route those addresses to you, >and you can use them as you choose.  You can't represent that "directly" in CIDR notation, but what it "probably" >means is that they are going to route 192.168.0.0/23 and 192.168.2.0/24 to you.  What you do with those addresses >and how you actually subnet them on your end is up to you, but you can NOT summarize them as "one" route unless >you have also been assigned 192.168.3.255, in which case you would have 192.168.0.0/22.

Ok, so for 192.168.0.0 - 192.168.2.255, would you represent this as 192.168.0.0/23 and 192.168.2.0/24? Am I correct in thinking that since this is a non-contigious block, it would actually be incorrect to write as 255.255.255.253?

Thanks again.

Got it, thanks very much for the excellent explanation