Solved

NETWORK MASK USING 255.255.255.248

Posted on 2010-09-09
2
504 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
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

Windows Server 2016: All you need to know

Learn about Hyper-V features that increase functionality and usability of Microsoft Windows Server 2016. Also, throughout this eBook, you’ll find some basic PowerShell examples that will help you leverage the scripts in your environments!

Question has a verified solution.

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

WARNING:   If you follow the instructions here, you will wipe out your VTP and VLAN configurations.  Make sure you have backed up your switch!!! I recently had some issues with a few low-end Cisco routers (RV325) and I opened a case with Cisco TA…
This article is in regards to the Cisco QSFP-4SFP10G-CU1M cables, which are designed to uplink/downlink 40GB ports to 10GB SFP ports. I recently experienced this and found very little configuration documentation on how these are supposed to be confi…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
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 …
Suggested Courses

617 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