This is happening quite a bit in ci, and causing spurious failures when it does. It makes it very difficult to merge patches that need to pass a lot of multinode jobs twice to get through the gate. For something like https://review.openstack.org/#/c/453127 that needs to pass 18 multinode jobs between the check and gate queue, it's next to impossible to merge it even though there's nothing wrong with the patch.
Example failure: http://logs.openstack.org/27/453127/1/check/gate-tripleo-ci-centos-7-scenario002-multinode-oooq/d803e64/
I'm guessing this is happening any time a job gets scheduled to an infracloud node. I believe I've seen discussion of the problem in IRC, but I couldn't find an existing bug.
There are 87 hits in logstash for this error: http://logstash.openstack.org/#dashboard/file/logstash.json?query=build_name%3A%20*tripleo-ci*%20AND%20build_status%3A%20FAILURE%20AND%20message%3A%20%5C%2215.184.64.1%20is%20not%20pingable.%5C%22 That's overreporting a little because some of the hits are duplicated, but I would estimate there are still at least 60 separate occurrences in that time frame.
2 hits in 24 hours, removing the alert.