Common operations at DCLIPv6OnlyHosting

How to check if a customer VM is alive?

There are many ways to check if a DCL VM is running/reachable. Here's the standard workflow:

  • First check: try to 'ping' the VM to see if it is up and reachable from the global Internet.
    • IPv6: ping -6 $IPV6_ADDR and (if available) IPv4: ping -4 $IPV4_ADDR
    • The VM is up and running if you get an answer, but ICMP requests (= ping) might be blocked by a firewall on the target or the target's networking might be broken: you'll have to switch to the next check.
  • Second check: find the VM on OpenNebula SunStone (= OpenNebula Web interface) under the Instances > VM tab and check its LCM State, which should be RUNNING if everything's alright. Try to open the VNC display (top-left VNC button once you have selected the VM) to see what's currently on screen (likely TTY login, which means the VM is up but does not say anything on networking).
    • If state is not RUNNING and VNC is unavailable/does not show anything, assume VM is down/blocked and requires (re)boot.
  • If the VM is up but does not answer to ICMP requests (= ping), try to see if there is any other open port with nmap.
    • nmap -6 $IPV6_ADDR (might take some time) will try to find open ports on the target. Try IPv6 and IPv4 (replace -6 by -4) if available, since some software/firewall default to IPv4-only. See the example below for a healthy service.
      • You can try to SSH if available, or to curl HTTP ports (curl http://$ADDR).
    • If ping does not work and nmap does not return anything, assume network is broken.

NMAP example

I ~ » nmap -6
Starting Nmap 7.80 ( ) at 2020-02-24 11:16 CET
Nmap scan report for (2a0a:e5c0:0:2:400:b3ff:fe39:7ba3)
Host is up (0.048s latency).
Other addresses for (not scanned):
rDNS record for 2a0a:e5c0:0:2:400:b3ff:fe39:7ba3:
Not shown: 996 closed ports
22/tcp  open  ssh
25/tcp  open  smtp
80/tcp  open  http
443/tcp open  https

Nmap done: 1 IP address (1 host up) scanned in 13.58 seconds

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Updated by ll nu over 4 years ago · 5 revisions