5.2 Troubleshoot client connectivity issues involving DNS

Before assuming it is a DNS problem test to see is DNS is working:

router#ping opens3.net
Translating "opens3.net"...domain server (192.168.122.1) [OK]
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 138.197.226.249, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 260/269/292 ms
router#

If your router/switch is able to convert a domain name to an IP address, DNS is working.
To troubleshoot DNS:

1. Test general network connectivity

router#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/46/60 ms
router#

2. Test reach-ability of DNS server

router#show ip dns view
DNS View default parameters:
Logging is off
DNS Resolver settings:
  Domain lookup is enabled
  Default domain name:
  Domain search list:
  Lookup timeout: 3 seconds
  Lookup retries: 2
  Domain name-servers:
    192.168.122.1
  Resolver source interface: GigabitEthernet0/0
DNS Server settings:
  Forwarding of queries is enabled
  Forwarder timeout: 3 seconds
  Forwarder retries: 2
  Forwarder addresses:

router#ping 192.168.122.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.122.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/13/28 ms
router#

3. Check ACLs

router#show ip access-lists