Oh! I got it now. The thing is, it is working exactly the way I thought it worked. I think it was just a matter of not being able to see the bit for the bytes. I just had to bit it out and it makes perfect sense. I forgot the mask doesn't tell me what my range is, but the combination of my IP address and my mask does. I forgot that a lot of people have the same netmak 112 is: 128 64 32 16 8 4 2 1 0 1 1 1 0 0 0 0 240 is: 1 1 1 1 0 0 0 0 Take an ip address in my range, say 115 which is: 0 1 1 1 0 0 1 1 To see if an IP gets "through" I would AND the other IP to my mask. Say 116: 0 1 1 1 0 1 0 0 - 116 1 1 1 1 0 0 0 0 - 240 ------------------------- 0 1 1 1 0 0 0 0 = 112, so is good (same when I mask my own IP) Take another one, like 161: 1 0 1 0 0 0 0 1 - 129 1 1 1 1 0 0 0 0 - 240 -------------------------- 1 0 1 0 0 0 0 0 = 160, not 112 so is no good. Regards, Jim Langston Larry Bolhuis wrote: > Jim, > > > I am told that my ip range is x.x.x.112 Block Size: /28 > > > > So, I have 112-140. My net mask is 255.255.255.240 > > You are misreading the x.x.x.112/28. This is cidr format and does not mean > .112 for 28 addresses but rather that of the x.x.x.112 when represented in >binary > the first 28 bits are NETWORK the remaining 4 bits are HOST. That means that > .112 is the network (in binary x.x.x.01110000). You have available addresses >up > to .126 (x.x.x.01111110) and .127 is the broadcast address (x.x.x.01111111). > > > wouldn't a mask of 255.255.255.240 mask off all bits but the last 4? > > Yup. > > > so wouldn't my range be from 0 to 15 with 0 and 15 being unusable? > > Yup again. But remember it's 112+0 to 112+15 (112 to 127) > > > Or is there something I don't understand about net masks? (I wouldn't > > doubt that). > > A subnet mask of 255.255.255.240 says the same thing as the /28. Lots of >ISP's > use the /28 cause it's quicker to write and is actually more easily >understood. > (Quick how many bits are on in 224? How about 248?) > > > Anyway, thanks for the help, but there is something funny going on, I think, > > with the AS/400 (or V3R7M0 in particular), IP address, netmasks and the > > internet. > > The funny part is not the AS/400. It is behaving as I would expect it to > except the part about NT and the router responding to PING. It is very strange > that if your NT box and Router each had the 255.255.255.240 mask that the >AS/400 > with a .139 address could ping them. Despite the fact that they are on the >same > physical wire they would have been on different IP subnets and as such should >not > have been able to communicate. If the AS/400 subnet was set at 255.255.255.0 > then the NT box may have responded (incorrectly) but any router worth it's > electrons shouldn't have. > > - Larry > > Jim Langston wrote: > > -- > Larry Bolhuis | What do You want to Reload today? > Arbor Solutions, Inc | Don't throw your PC out the window, > (616) 451-2500 | throw WINDOWS out of your PC. > (616) 451-2571 -fax | Two rules to success in life: > firstname.lastname@example.org | 1. Never tell people everything you know. > +--- > | This is the Midrange System Mailing List! > | To submit a new message, send your mail to MIDRANGE-L@midrange.com. > | To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com. > | To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com. > | Questions should be directed to the list owner/operator: email@example.com > +--- +--- | This is the Midrange System Mailing List! | To submit a new message, send your mail to MIDRANGE-L@midrange.com. | To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com. | To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com. | Questions should be directed to the list owner/operator: firstname.lastname@example.org +---
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