Need to backup remote database using mysqldump
Unfortunately, you cant continue your failed backup. When mysqldump returns a failed status you have to start over again.

My first recommendation is to compress your script before transmitting it 

mysqldump -h 192.168.10.209 -u user -ppassword testdb | gzip &gt; dump.sql.gz


Another recommendation is to connect to the remote server via ssh, then make the backup in the remote server (never will fail for network issues because is a local backup) and, in the last step you could transmit the file (after compress of course).

Other than that, the other 2 options more used are PERCONA XTRA BACKUP and MYSQL ENTERPRISE BACKUP but there are also high prices involved.