I have been forwarded a complaint from an international user who can’t access my company’s Web site. Even though this is just one user, management wants this dealt with. The complaint in the e-mail, as best I can understand it due to the language difference between the international user and myself, is that they are getting a page cannot be displayed. No one else has reported this problem. How would you suggest resolving this problem?
— Via the Internet.
I would ask the user a few questions: What is his IP address when on the Internet, the IP address of the DNS servers he is using and the browser being used for starters. If he isn’t sure of what his address is or is behind a firewall, you can have him go to www.ipaddressworld.com and that will get that for him easily. Once you get the IP address, I would do a quick lookup on www.arin.net. This should tell you what ISP and country the connection is coming from. This is dependent on the ISP properly registering the information with the coordinating registrar for their country. If you aren’t able to find any cause for the problem at your end, you may need to do some checking with the originating ISP to see if they may have an issue at their end.
With the address supplied by the user, look at your firewall(s) and DNS servers at your end to see if this address or a range that this address could be in are getting blocked for any reason. Depending on the type of IPS/IDS system you could have in place, the address could have been blocked due to a perceived attack coming from that address. Check the logs on the respective network equipment at the boundary of your network to look for any access attempts coming from this address.
Do an nslookup on the DNS servers that the remote user is working with. See if you can get resolution on the host name of the web server that the user is trying to access on your site. If you can’t get resolution, this could be an issue that will have to be addressed by remote user’s ISP. If everthing checks out so far, try entering the users IP address at www.dnsstuff.com and www.traceroute.org. Doing a traceroute from dnsstuff.com will let you see if a good path exists between the location of dnsstuff’s servers and where the remote user is. Traceroute.org offers the same service but with a twist: You can choose from a list of countries and locations in a country where to run a traceroute from. Also try to run a traceroute from the country where the user is located to see if there is a route problem between that country and your server.
From what you describe, it shouldn’t be too hard to find the problem. Using the steps I have listed here will help you to begin to isolate where the problem may be and potential cause(s) for it. Bookmark the Web sites I have listed here future use, you may need to call upon them again at some point.
