Scenario: A Sonicwall TZ170 (standard firmware) was replaced with a TZ215 (Enhanced ). After installation we could not establish a connection to the main Oracle DB over a site-to-site VPN. Pings and all other services were working fine.
To get this working go to Firewall Settings -> Advanced
Select SQL*Net From Enable FTP Transformations for TCP port(s) in Service Object
Disable Enable support for Oracle (SQLNet)