Solved

NETWORK MASK USING 255.255.255.248

Posted on 2010-09-09
2
498 Views
Last Modified: 2012-05-10
We have a customer who has their T-1 provided by Paetec.   Paetec also provides our T-1 service.  As it turns out, our customer is on the same subnet as we are.  Both of us are on 63.252.84.xxx and problem is they cannot reach our webserver.   Paetec suggested we change our network mask from 255.255.255.0 to 255.255.255.248 to fix the issue.

I would love a clear understanding of why this will make it all workable?   Paetec could not or would not explain, just said do it.
0
Comment
Question by:Lance McGrew
2 Comments
 
LVL 33

Accepted Solution

by:
Todd Gerbert earned 500 total points
ID: 33639954
To over-simplify a bit ... the network mask allows for the division of an IP network into several smaller networks.
The subnet mask you should be using is given to you by the network administrator, in this case you're talking about the T1 network (which really is it's own network with two devices, your router and Paetec's router), and since Paetec is the administrator of that network you should be using the netmask they've given you - it's not something you get to "just choose" - it has to be what you're told to use.
Really, you are not on the same subnet as your customer - they are on the 63.252.84.0 - 63.252.84.3 network, and you're on the 63.252.84.4 - 63.252.84.7 network (each network has only 4 IP addresses), but since you're using the wrong netmask your router wrongly thinks 63.252.84.0 - 63.252.84.3 is on the same network, so it doesn't route packets the way it should.
Hope that makes some sense - your question is fairly broad, and routing/IP addressing can be somewhat involved.
0
 
LVL 3

Expert Comment

by:kf4zmt
ID: 33639965
The subnet mask is what separates the host part of an ip address from the network part.  It looks like in your case your isp has split a class b network into multiple subnets to assign out to their customers.  When both you and your customer use the correct subnet mask, you won't actually be on the same subnet. Unless of course your isp has made a mistake but this is unlikely.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Quality of Service (QoS) options are nearly endless when it comes to networks today. This article is merely one example of how it can be handled in a hub-n-spoke design using a 3-tier configuration.
Getting hacked is no longer a matter or "if you get hacked" — the 2016 cyber threat landscape is now titled "when you get hacked." When it happens — will you be proactive, or reactive?
Both in life and business – not all partnerships are created equal. As the demand for cloud services increases, so do the number of self-proclaimed cloud partners. Asking the right questions up front in the partnership, will enable both parties …
Both in life and business – not all partnerships are created equal. Spend 30 short minutes with us to learn:   • Key questions to ask when considering a partnership to accelerate your business into the cloud • Pitfalls and mistakes other partners…

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

25 Experts available now in Live!

Get 1:1 Help Now