While I’ve had most of my services IPv6 enabled for quite a while, I have not set up monitoring of those services over IPv6 yet. This blog post is a summary of my experiences IPv6 enabling my nagios setup.

Defining IPv4/v6 specific service checks

All of my servers run Debian and as such, my nagios config is a little Debian-centric. The nagios-plugins-contrib package defines some useful generic and IPv4 specific commands under /etc/nagios-plugins/config. For example, the file /etc/nagios-plugins/config/mail.cfg defines both check_simap as well as check_simap_4 (explicit -4 on the command_line).

I found it useful to define IPv6 specific check commands as well, so for example I’ve created check_simap_6 which is identical to check_simap_4 except its got -6 instead of -4 to force v6 checking.

One interesting issue I came across is that the host check can only be performed over IPv4 OR IPv6. Your environment will one primary address family. If you have v4 for the primary check, and have a v6 only host, you’d need to define a custom check command for the host, or perhaps an IPv6-only host template which you could apply instead of generic-host.

DNS Matters

To simplify checks, using dual-stacked hostnames is a MUST. By ensuring address is set to a dual-stacked host name we can use our checks which force -4 or -6 and ensure the check is happening over the proper address family.

Custom Variables

For checks which I prefer to use a literal IPv4 or IPv6 address, I’ve defined IPv4 and IPv6 address variables. _ADDRESS4 and _ADDRESS6 which are usable as $_HOSTADDRESS4$ and $_HOSTADDRESS6$. I am only using this for DNS server checks at the moment, so that if DNS fails for some reason I’ll still be able to monitor my nameservers.

An example of this:

define host{
  use         generic-host
  host_name   nagios.ciscodude.net
  alias       nagios.ciscodude.net
  address     nagios.ciscodude.net
  _ADDRESS4   45.63.67.34
  _ADDRESS6   2001:19f0:5c00:960e::64
}

IPv4-only Check Plugins

Encountered check plugins that are v4 only:

• check_icmp which I actually prefer to check_ping, however check_ping is v6 compatible (and has a -6 flag)