Icinga is receiving and correctly reporting nsca reports for frbast2001, so we know frbast2001->icinga-server is working. However the host-up check is failing, which I believe is icinga-server->frbast2001.

I found and fixed the IP for frbast2001 in the icinga config, and also adjusted the subnet definitions in data.yaml to reflect the changes in T204271, and by now I think if this were the issue it would have resolved. Still no luck.