node_exporter listen only ipv6

[Kosm0]

I install node_exporter on new, clear CentOS 7.2.1511

netstat -antp | grep LIST
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1328/sshd
tcp6 0 0 :::9100 :::* LISTEN 10804/node_exporter

/etc/systemd/system/node_exporter.service
[Unit]
Description=Node Exporter

[Service]
User=prometheus
ExecStart=/home/prometheus/Prometheus/node_exporter/node_exporter

[Install]
WantedBy=default.target

/etc/sysctl.conf
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

[brian-brazil]

That's a Linux thing. I've never figured out why it happens but it's harmless and will respond on ipv4.

[horazont]

See the ipv6 manpage in section 7:

IPV6_V6ONLY (since Linux 2.4.21 and 2.6)
       If this flag is set to true (nonzero), then the  socket  is  re‐
       stricted  to  sending  and receiving IPv6 packets only.  In this
       case, an IPv4 and an IPv6 application can bind to a single  port
       at the same time.
       
       If this flag is set to false (zero), then the socket can be used
       to send and receive packets to and from an IPv6  address  or  an
       IPv4-mapped IPv6 address.

       The argument is a pointer to a boolean value in an integer.

       The  default  value  for this flag is defined by the contents of
       the file /proc/sys/net/ipv6/bindv6only.  The default  value  for
       that file is 0 (false).

It allows an application to bind to :: and serve IPv6 and IPv4 with a single socket. IPv4 peers are mapped into the IPv6 address space using the prefix ::ffff: followed by the IPv4 address. Totally harmless, and would go away if you explicitly bound to 0.0.0.0 (but that would prevent IPv6 from being used).

[brian-brazil]

Thanks for the explanation!

[Bluscream]

I have the same issue but my prometheus instance can't connect to the IPV6 port