Understanding 'Connection Control' under SMTP Virtual Server properties

This involves Exchange Server 2003 (Enterprise) using an internal IP range of 192.168.100.x.

When building the Exchange server, I wanted to limit connection access to a single IP range outside of the network (a hosted spam filtering service) and to the internal network range.  I went to:  

SMTP Virtual Server Properties > Access > Connection (Connection Control) Connection

I checked "Only the list below" and first entered an IP range that the hosted provider offered.  I wanted to further open access to only our internal range and so I entered "192.168.0.0 (255.255.255.0)".  This didn't work as a "blanket range" - instead I had to enter "192.168.100.x (255.255.255.0)".

The reason is probably very simple, but can someone help me understand why 192.168.0.0 would not work?  I was assuming that it would envelope 192.168.100.x.

Thanks.
james_axtonAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

AkhaterCommented:
192.168.0.0 255.255.0.0 would include the 192.168.100.0

192.168.0.0 255.255.255.0 means from 192.168.0.0 to 192.168.0.255
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
james_axtonAuthor Commented:
Akhater, forgive me, but those two statements seem to contradict each other.  I'm sure they don't though - so can you help me understand?
0
AkhaterCommented:
it depends on the subnet mask
A subnet mask of 255.255.255.0 will "include" only the last octet so from 192.168.0.0 to 192.168.0.255
A subnet mask of 255.255.0.0 will include the last 2 octets so from 192.168.0.0 to 192.168.255.255

here is an IP subnet calculator http://www.subnet-calculator.com/ it might help
0
james_axtonAuthor Commented:
Oops, I missed the subnet change the first time I read your post.  Now I see my mistake - I used "192.168.0.0 (255.255.255.0)" instead of "192.168.0.0 (255.255.0.0)".  The latter would have worked with our range of 192.168.100.x; the former, as I learned, did not work.  Am I reading it correctly now?
0
AkhaterCommented:
"192.168.0.0 (255.255.0.0)".  would have worked you are right
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Email Protocols

From novice to tech pro — start learning today.