I have a few Synology NAS at work which are used for storage. I have been locking down the firewall on them to only allow certain ports from specific IP subnets. However, I still wanted to be able to ping the Synology from anywhere. I couldn’t work out how to configure the Synology firewall to let through pings ( ICMP messages).
You have to go to: Control Panel -> Security -> Firewall -> Create:
Under ports select Custom and then under protocol select ICMP.
Press OK a few time and then Save the firewall settings. You should then be able to ping the NAS without any problems.