Show pageOld revisionsBacklinksBack to top This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong. ====== Troubleshoot DNS Client Issues ====== **General Information** Client perspective checking DNS configuration. ---- ====== 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 ---- ====== Troubleshooting: Unbound ====== View (dump) the current contents of the unbound cache <code bash> unbound-control dump_cache </code> * This can be also redirected to a file to make edits and load back into cache \\ Purge the cache: Single record <code bash> unbound-control flush myhost1.example.com </code> \\ Purge the cache: Entire Zone <code bash> unbound-control flush example.com </code> \\ Load cache from a file (dumped there previously) <code bash> unbound-control load_cache < cache.txt </code> ---- ====== Troubleshoot DNS From a Client ====== Check to see what DNS servers are configured <code bash> cat /etc/resolv.conf </code> * 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/ \\ Ensure a route exists to the DNS server <code bash> ip route sh </code> \\ Ping the DNS server <code bash> ping -c4 <ip-of-dns> </code> \\ Check to see if you can connect to port 53 <code bash> telnet <ip-of-dns> 53 OR nc -v -w 3 <ip-of-dns> 53 </code> \\ Test a domain lookup against the DNS server directly <code bash> dig @<ip-of-dns> google.com </code> \\ 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 ---- linux_wiki/troubleshoot_dns_client_issues.txt Last modified: 2019/05/25 23:50(external edit)