Why is there an error in rsync?

Question

linux

Good afternoon. There is a file server on which a bunch of everything runs (on centos), there is a backup server (suse) on which rsync is run once a week for samba backup, etc.
Today backup stopped working, rsync complains like this:
NAS:~ # rsync -az --delete [email protected]:/home/samba/data/ /mnt/Backups/data/ --progress
ssh: connect to host 10.11. 4.100 port 22: No route to host
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: unexplained error (code 255) at io.c(235) [Receiver=3.1.0]
Configuration not changed, only NAS turned off.
After 20 minutes, everything worked itself out.
Where to look to find out why it didn't work? I would like to know where the problem came from so that I know what to treat.

Answer 1

No route to host - there is no route to the destination address.
Is it on, route active, ports open?