If Page Not Found - August 2009

Improvements

We are moving to a completely redundant Internet connectivity system. 
Currently all our internet communication and server communication travels over two different  IP sets, either 70.182.102.x or 75.13.188.x, but everything is moving to a new set 216.176.33.x to 216.176.47.x. That provides us 3825 usable addresses. Under our old architecture, if one connection fails everyone has to manually failover to the backup addresses and IT has to change gateways on the servers.  This new system is a very expensive and substantial  improvement for us. This new type of connectivity and redundancy called Boarder Gateway Protocol (BGP) is more than or equal to what most Internet Service Providers have.  With this new system we will never have to change our IP's AND if one connection to the Internet fails the other picks up automatically, with no human intervention. This comes at a cost of purchasing double the bandwidth needed from two different service providers, purchasing IP's and ASN numbers from ARIN, two expensive redundant CISCO routers and two redundant CISCO firewalls.     

Issues

DNS can take up to ten days tp propagate to everyone, making sites appear to be offline.
DNS maps the human-readable name (DNS) to the computers IP number.   For example, demo.mysoapware.com was linked to the IP of 75.13.188.60 and is now moving to 216.176.33.60.   This would cause no issues if every Internet Service Provider and every local IT Department updated their DNS every 10 minutes like our DNS servers are set to do. Our Time To Live (TTL) on our DNS names are set to 10 minutes, which means after 10 minutes has past if the end user wants to go to the address again, it has to look it up on our DNS servers. With this low setting any change in DNS should only take a maximum of 10 minutes to update.   Reality is often different, users will request a DNS name such as the demo.mysoapware.com and get the old DNS from their Internet Service Provider, as they cache out these addresses to reduce outboud traffic. In these cases there is nothing they can do to make their Internet Service Provider update, but there are a few things to do on the users computer to overcome the failure.

Here is a list of DNS's that might fail in August 2009:

#Electronic Prescriptions
216.176.33.119     swwebservice1.com 

#Web site
216.176.33.123     www.soapware.com  

#web site
216.176.33.123     soapware.com  

#Faxing service
216.176.33. 219    fax.mysoapware.com 

#Customizations Library 
216.176.33.61    Lib.mysoapware.com 

# Drug Interactions
216.176.33.147    swwebservice4.com 

# Clinical Knowledge
216.176.33.107    proxy.mysoapware.com 

#Licensing Server and Bug Reporting
216.176.33.27    lic.mysoapware.com 

#Error reporting (FogBugz)
216.176.33.90    swwebservice2.com 

#Bug Reports (HelpDesk)
216.176.33.118    helpdesk.mysoapware.com

#Swoogle (index for soap
216.176.33.210    swoogle.mysoapware.com

Key Terminology

DNS: Domain Name Systems, humans have difficulty remembering long numbers so DNS was devised to make it easier to remember addresses to servers. For instance, if I asked you to remember SOAPware.com, most of you could do that, but if I asked you to remember “216.176.33.123” my guess is you’d forget it before you got to the end of this article.   DNS matches a name (Domain Name) to the number (IP Address).  Computers on the other hand have the opposite problem, they don’t know what to do with a name they use numbers to communicate, so the DNS servers where devised.  A DNS server provides the number for a given name.  On your computer you type in the name of the server, and the computer then goes out to a DNS server and says, “DNS  server, provide me the number to SOAPware.com”, the DNS server answers back with, “the number is 216.176.33.123”. Then and only then can your computers find and communicate with the server SOAPware.com.   (This is an over simplification, but adequate for our needs)

TTL: Time-To-Live, Server's numbers (IP addresses) can change, and do quite often, but we don’t want to make every person remember a new server name when this change takes place. Can you imagine the loss of revenue if google.com changed its domain name every time they upgraded to a new computer number over the years?  google.com, then google2.0.com then google3.0.com… It would be a marketing nightmare and totally confusing for the end user.  So a Time-to-Live was introduced to the system. TTL says, after “x”amount of time go back to the DNS server and look up the server's number. This way an IP address can change and the DNS will receive the new updated number.

DNS Mappings: A DNS entry or mapping is the single entry in the DNS server that associates a single server name with a computers number. An example would be “soapware.com   216.176.33.123”..

IP: Internet Protocol is a protocol used for communicating data across a network. Many refer to a single IP number assigned to a computer as the IP number or an IP address.  The IP address or number is made up of four sets of numbers separated by dots, for example “216.176.33.123”.   These numbers are how both private networks and public networks (Internet) know how to route data communication. . 

Cache: In reference to DNS, “cache” is a local repository of DNS mappings or entries held on computers to speed up name to IP resolution.  This repository keeps the computer from going all the way out to the DNS servers every time a server name is requested.  Ideally, this cache should never to be longer than the DNS’s TTL, but often it can be.

Ping: No one is for sure where it came from, but the term refers to the old sonar pinging for submarines. When trying to hunt for the other sub they sent out a sound that literally sounded like a P-i-n-gggg.  Today, it’s a way to test if the computer is available, you ping a computer name, it looks to DNS to get the IP address, then it sends the server or computer a small request asking, “are you there”  if it’s there and can reply, it does. The resulting ping back lets you know the computer is there and how long it took to make the trip.

SOAPware Support's Instructions

1. Verify they are getting an old DNS, if they ping the DNS name and it starts with 70 or 75 you know it's bad, if it receives a 216 number DNS is not the issue.

2. Reboot the computer if possible to flush the DNS. If the computer can't be rebooted then run the command line command of "ipconfig /flushdns".

3. After a reboot or the flush of DNS,  Ping the DNS name again, if it fails, ask them if they are on a domain server, if they are then ask them to run the "ipconfig /flushdns" on the domain server.  After the server has flushed the DNS ask the user to flush the DNS one more time to make sure it's not remembering the old DNS entry. Ping the DNS again. 

4. If after step 3 the user still does not have an updated DNS, we will have to enter the new DNS name in their HOSTS file or wait up to 10-days for it to propagate to them.  

• The file is located in the C:\WINDOWS\SYSTEM32\DRIVERS\ETC folder, Start > My Computer > C:\drive > Windows folder > System32 folder > Drivers folder > etc > look for HOSTS.  
• First make a copy of the HOSTS file incase you damage it.  
• The filanme is HOSTS & has no extension, when double clicked you will receive a "Open With" dialog, choose the application "Notepad" and click OK.  

• When it opens you'll see a list of notes with "#" signs, these represent a note or what is called a REM statement, it keeps the computer/application using the file from reading that line, usually these lines are for people to read so that the code can be understood.  The lines without a "#" are DNS mappings.  If you see a line like "127.0.0.1  localhost" this expression is telling the computer that 127.0.0.1 maps to the name "localhost".  In our example we would want to map the IP of 216.176.33.60 to the DNS name of demo.mysoapware.com.

The new line would look like this: 

Put your mappings after the 127.0.0.1 line, if there is one, but near the top if it ever has to be found or changed again.  Save the HOSTS file, but do NOT ping the DNS name that was entered again, if it doesn't go out to check the internet for the IP address, the HOSTS file is the first place DNS looks.