... mechanism, including online detect, auto redial when offline to make router always onlineEthernet port: 1.5KV magnetic isolation protectionRS232/RS485/RS422 ... (PPTP,L2TP,IPSEC and GRE)(only for VPN version)Support multi online trigger ways, including SMS, ring and data. Support link ... server and client, DDNS, firewall, NAT, DMZ host etc.Support multi protocols, such as TCP/IP, UDP, ICMP, SMTP, HTTP, ...