For several weeks now, several employees at my company and some of our customers have been reporting problems with getting access to our Web sites and e-mail. The only common thread is that they all use the same ISP, a local cable internet provider by the name of Insight. No other customers or employees have reported this same problem with any other ISP.
For several weeks now, several employees at my company and some of our customers have been reporting problems with getting access to our Web sites and e-mail. The only common thread is that they all use the same ISP, a local cable internet provider by the name of Insight. No other customers or employees have reported this same problem with any other ISP. To me, this would indicate an ISP level problem but I dont have anything that would concretely confirm that. I have tried talking to their technical support and finally got to someone in technical support who kept saying it was a Bogon problem. What is Bogon? Do you have any suggestions?
— Via the Internet
You are not the only reader to have reported this same issue. After doing a little digging, I found out something interesting. Insight recently changed the ISP they were using to connect to the Internet. For some time, they had been using AT&T and had been giving out a 12.x.x.x address to their customers. After the provider change, the IP range being handed out to Insight internet customers changed to a 74.x.x.x address range.
While this may not sound like much, this may explain some of the problems you are seeing. When an IP address range, either in total or in part, is not assigned to an ISP or is not in use by the assigned ISP, it ends up on what is a Bogon list. This is a list of IP ranges/subnets that are available for any network admin to use to block access to their network so as to try to avoid IP addresses that arent in use from being spoofed and possibly causing denial-of-service or other network attacks. See this site for more information. With this information in hand, see if any of your DNS servers are making use of a Bogon list or are otherwise blocking requests from specific IP address ranges. Remove the 74.x.x.x address range from your DNS servers and or firewall access control lists if you find this address range showing up. Check the address ranges you are blocking again on the Bogon site above – ideally at least once a week. If you don’t see any problems, check the ISP that your company is using to see if they have this IP address range in their Bogon list and get them to delete it. If you have found IP range mentioned in your systems and have deleted it and are still having problems, or didn’t find it and are still having problems, there is one more thing that you can look at. Insight seems to be using up to 5 different DNS servers that its customers are assigned to use based on that is handed out by Insights DHCP server. When you have users are reporting problems with accessing your Web sites/e-mail and are on the Insight cable connection, have them look up on their PCs or firewalls to see what DNS servers have been assigned to them. Using the NSLOOKUP command, probe those DNS servers to see what type of information they are or aren’t handing out regarding the various hosts that have DNS assigned by your DNS servers. You may find that one or more of the Insight DNS servers are either timing out or not coming back with IP addresses when prompted to resolve from a fully qualified domain name.
If you see this, try moving the users in questions to statically assigned DNS servers hosted by someone else. If this finally fixes your problem, this would seem to indicate that there may be a secondary problem with one or more of the DNS servers being used by Insight. You will need to do some detective work on your part to see what the problem(s) may actually be for you. If you cant find anything on your network that explains this problem, ask to speak to a technical support supervisor at Insight and see if you can get them to work with you on resolving the problem.
