At approx 10:35pm this evening, one of our core Cisco routers unexpectedly rebooted.
This was due to an IOS-XE crash. The router automatically restarted, and BGP sessions will re-establish.
Some network instability would have occurred during this restart due to the unclean nature of the reboot.
We will investigate the logs and any core dumps, and schedule maintenance if needed (it may require a firmware upgrade if this is a known Cisco bug)