We encountered an issue where a series of git requests over ssh would sometimes fail with
ssh_exchange_identification: Connection closed by remote host
There are many examples on SE/SF of structural problems (tcp-wrappers, permission on key files).
Our problem was: What is a likely cause of intermittent connection failures with this message?
Our issue appeared to have been caused by a moderately high number of incoming requests.
As soon as the number of unauthenticated connections goes over the sshd:MaxStartUps parameter, sshd starts rejecting those connections.
The solution lies in modifying
MaxStartupsinsshd_config