When a user (public or private) is unable to access certain Web sites or Web pages, what is the first thing I should...
do to try to locate and resolve the problem? Also, what basic steps should I walk the user through to help them try to resolve the problem themselves in the future? My understanding is that you have a Web server, to which users from the private or public are trying to access, but are unsuccessful. So where do we start from?
Firstly, in most situations like this the problem tends to be the server itself. The reason being, it could be considered somewhat normal for the general public to be unable to access the server if the firewall/router hasn't been configured to allow this type of access. For internal users, however, it's highly unlikely to be a firewall problem unless it actually exists!
Here are my suggestions: Find out if there is a firewall between (a) the Web server and the public, and (b) the Web server and the private network.
If there is a firewall in both cases, then place a workstation on the same network as your Web server and try to access it. If successful, this means that your Web server is working correctly. If not, then you've most likely found the problem!
Assuming that there's no firewall between the Web server and the private network, and all services on your Web server are running correctly, try to ping the Web server. If a ping works, then there is logical connectivity to the server. If a ping doesn't work, then you have a bigger problem. In that case, try to perform a trace route or physically inspect the nodes your packet would travel until it reaches the local Web server in order to see if there is physical damage, e.g. the switch connecting the Web server might be disconnected from the rest of the network!
Before you deal with the public users, you should ensure that the private ones are able to access the Web server because if local users can't access the Web server, there is a good chance public users won't be able to either.
Critical services required to access a Web server are: DNS and HTTP. Ensure that the DNS server is properly resolving the Web server internally and that the IIS service on the Web server is running!
Whichever way you choose to troubleshoot your problem, I'd suggest you start from the closest point to the server and work backwards towards the public users.
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