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Network configuration flaws block server access and wireless printing

I am working in a real estate company, which is part of one big group. We have 50 users here and a small server room for data storage and Internet. We are running our Internet through our wireless link from our big group head office, and email exchange is also there but we have only a small domain controller. I also have a third party ISP DSL Internet, which helps me when our link with the head office is down.

The problem is, if the link goes down and everyone uses DSL through wireless, then they cannot print, cannot access the server machine, because the network and IP are different.

I need to merge DSL connection with my local network so when the link is down and users are using DSL, they can print at the same time and they can access server folders. Note: I have DHCP IP.

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It seems to me that there are a number of things that are probably causing printing problems that you can avoid. It seems you've actually stumbled upon one of those epic IT questions: Is it really the network? Or could it be something far more nefarious like the application infrastructure? Perhaps you will be just the network engineer to solve this! In all seriousness, from your question, it sounds like the DHCP scopes should be transparent to the routing uses to uplink you to the Internet and the head office. I've tried to draw a basic diagram of the network you described below:


Click the image to view a larger diagram.

As long as the user network is sending traffic through the router, the router should be making the routing decisions about path availability. Based on your description, when the route to the head office is down, the issue appears to cause printing and file server access to be terminated. One of the first things I would do is re-direct printing and server access requests to the small domain controller transparently.

However, I truly suspect that the issue is not really a network-IP issue but more of a configuration issue on the Windows authentication and directory access-side. Remote domain controllers exist to provide authentication and printing services to remote offices when the head office is not accessible. It sounds like authentication requests and printing services are still going to the head office Active Directory (AD) server before being transmitted to the local domain controller and printer. To verify, ensure that the domain controller has access to synchronize the AD catalog and authenticate users. I would ensure that the domain controller is set up correctly and then purposefully disconnect from the head office (after hours to not interrupt business day activities of course) to test whether this fail-safe method works.

Ideally you'd rarely have to have head office access to print locally with this configuration. I would provide you a few more details but it depends on the version of domain controller and your AD setup as to how to accomplish this. May the force be with you though! And have some great AD fun.

This was first published in April 2009

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