In this hands-on lab, we will walk though troubleshooting DNS resolution issues on the provided host.
Learning Objectives
Successfully complete this lab by achieving the following learning objectives:
- Verify the Issue and Check `/etc/nsswitch.conf`
We’ll first need to verify that the issue exists by attempting the
curlthe header ofacloudguru.com:curl -I https://acloudguru.com/Then we need to verify that nothing is missing in this file, and we should pay attention to the ordering of the
hostsvalue:hosts: files dns myhostname- Verify `/etc/hosts` Contents
We’ll want to make sure there aren’t any entries in this file that would cause issues:
cat /etc/hosts- Determine If the DNS Host is Listening on TCP Port 53
If the host is listening on TCP port 53, we’ll know by running this:
telnet 10.0.1.1 53- Check Resolution Using the 10.0.0.2 DNS Host
Now that we’ve verified that the host listed in
/etc/resolv.confisn’t available on TCP port 53, check if resolution is working on the DNS host10.0.0.2:dig @10.0.0.2 acloudguru.com- Change the Configuration to Use the 10.0.0.2 Host
We can do this with network manager, or by editing
/etc/resolv.conf. If we restart networking, this is the IP that will be used via DHCP. Remove the10.0.1.1entry.
