====== Troubleshoot DNS Client Issues ======
**General Information**
Client perspective checking DNS configuration.
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====== Lab Setup ======
The following virtual machines will be used:
* server1.example.com (192.168.1.150) -> Perform all connectivity tests from here
* server2.example.com (192.168.1.151) -> Install DNS caching here
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====== Troubleshooting: Unbound ======
View (dump) the current contents of the unbound cache
unbound-control dump_cache
* This can be also redirected to a file to make edits and load back into cache
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Purge the cache: Single record
unbound-control flush myhost1.example.com
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Purge the cache: Entire Zone
unbound-control flush example.com
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Load cache from a file (dumped there previously)
unbound-control load_cache < cache.txt
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====== Troubleshoot DNS From a Client ======
Check to see what DNS servers are configured
cat /etc/resolv.conf
* Take note of whether the file is controlled via NetworkManager. If so, then the DNS servers are set via that service/from /etc/sysconfig/network-scripts/
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Ensure a route exists to the DNS server
ip route sh
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Ping the DNS server
ping -c4
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Check to see if you can connect to port 53
telnet 53
OR
nc -v -w 3 53
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Test a domain lookup against the DNS server directly
dig @ google.com
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Dig returns a status indicator in the "Got Answer" section. Values can be:
* NOERROR - DNS resolve was successful
* NXDOMAIN - DNS info requested could not be found
* SERVFAIL - Error contacting a DNS server
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