Cause: the 9100 port is blocked on all nodes by default.
Consequence: Prometheus can't scrape the node_exporter service running on the other nodes and which listens on port 9100.
Fix: the firewall configuration is modified to allow incoming TCP traffic for the 9000-1000 port range.
Result: Prometheus can scrape the node_exporter services.
# netstat -anlp | grep 9100
tcp6 0 0 :::9100 :::* LISTEN 5869/node_exporter
tcp6 0 0 172.16.120.79:9100 172.16.120.57:36830 ESTABLISHED 5869/node_exporter
and node-exporter target could be accessed without error, see the attached picture
openshift-ansible version: 3.10.29-1
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2018:2376