This section describes how to troubleshoot issues with the IP and DNS traffic on a VM.
To verify the IP traffic:
Log in to the VM in question.
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
If pinging does not work, use the traceroute command on the same address to identify the issue.
To verify the DNS traffic:
Log in to the VM in question.
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
.
If the domain to the IP address is not resolvable:
Run the following command to identify when the resolve of the DNS server stops:
dig google.com +trace
Dig a different server name. For example:
dig google.com @8.8.8.8