The first session of the week is “DNS Demystified.” All OSX systems really like Good DNS, and it has been critical for me, as your system admin, to make sure that DNS is configured properly.
It’s always good to sit in a refresher session, and any would be Mac admin needs to have a solid understanding of DNS.
This morning my ISP, which is normally very reliable, had a network issue. As part of managing a network I don’t ever throw my hands up and say “they have a problem and they’ll fix it.” I generally determine what the problem is at the same time. This way, I am confident that that problem is not something I did, while at the same time I am also able to report information back to the ISP that could be critical to repairing the problem. I have several guidelines that I go through as I work through a network issue:
- Start by identifying potential problems on your own computer and work toward the cloud. This means asking someone else on the same network if they are having problems. If they are not, it is something about your computer, and you should look into it rather than troubleshoot the network any further. There are a few cases where a network issue will affect one computer, but they are rare.
- Check your network connection. If you don’t have a wireless signal or your ethernet switch is crashed or shut off you won’t get far.
- Check the IP address of your local router. Generally these have a web interface and the IP address is the “Router” address in the “Network” System Preference. Use a web browser and see if it loads a webpage.
- Check the link to the ISP. Now that you have a link to the router, it should list whether the link is up or down. If it is active the problem is not on your network, and you should call the ISP to notify them of a problem and skip to step 6.
- If it is down, check the connections on the back of the router. DSL will have a phone connection, Cable will have a coax connection. Make sure they are connected to the proper location on the wall.
- Check DNS. I generally know the IP address of some pingable addresses on the internet. For instance, I know that www.google.com is located at 188.8.131.52, so I can try entering “ping -c 10 184.108.40.206” into terminal.app (which can be found in your Utilities folder) and see what percent of the 10 ping packets are received. If it is 0% loss, the issue is DNS. If it is 100% loss, it is a routing issue.
For each level of issue, there are a few things to try:
- Computer – reboot, make sure that DHCP is giving the computer an address.
- Computer-Network Link – reboot switch, make sure configuration is what is to be expected
- Router – reboot router, make sure configuration is what to be expected
- Router-ISP Link – call ISP, wait
- Premise wiring – reconnect wiring
- DNS – configure computer/router to use an alternate DNS server, such as Google’s Public DNS (220.127.116.11 & 18.104.22.168)
- Routing – Map out where you can get and where you cannot, using traceroute and ping
Naturally, network issues are one of the problems that Evolve cannot assist with using Screen Sharing session. We can assist over the phone, and work very closely with you and your ISP to determine and resolve the problem in a timely manner.