Verify the IP and DNS traffic¶

This section describes how to troubleshoot issues with the IP and DNS traffic on a VM.

To verify the IP traffic:

1. Log in to the VM in question.

2. Ping any IP, for example, Google DNS 8.8.8.8:

   ping 8.8.8.8 -c 3
   

   Example of system response:

   PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
   64 bytes from 8.8.8.8: icmp_seq=1 ttl=59 time=4.12 ms
   64 bytes from 8.8.8.8: icmp_seq=2 ttl=59 time=4.37 ms
   64 bytes from 8.8.8.8: icmp_seq=3 ttl=59 time=4.03 ms
   
   --- 8.8.8.8 ping statistics ---
   3 packets transmitted, 3 received, 0% packet loss, time 2002ms
   rtt min/avg/max/mdev = 4.038/4.180/4.377/0.161 ms
   

3. If pinging does not work, use the traceroute command on the same address to identify the issue.

To verify the DNS traffic:

1. Log in to the VM in question.

2. Run the following command:

   dig google.com
   

   Example of system response:

   ; <<>> DiG 9.9.5-3ubuntu0.16-Ubuntu <<>> google.com
   ;; global options: +cmd
   ;; Got answer:
   ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15428
   ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 5
   
   ;; OPT PSEUDOSECTION:
   ; EDNS: version: 0, flags:; udp: 4096
   ;; QUESTION SECTION:
   ;google.com.                    IN      A
   
   ;; ANSWER SECTION:
   google.com.             300     IN      A       216.58.201.110
   
   ;; Query time: 20 msec
   ;; SERVER: 172.17.32.194#53(172.17.32.194)
   ;; WHEN: Thu Nov 23 14:14:41 UTC 2017
   ;; MSG SIZE  rcvd: 191
   

   In the output above, the VM resolved the google.com domain to the IP address 216.58.201.110.

3. If the domain to the IP address is not resolvable:

   1. Run the following command to identify when the resolve of the DNS server stops:

      dig google.com +trace
      

   2. Dig a different server name. For example:

      dig  google.com @8.8.8.8