Description:
This article describes best practices for creating firewall rules on a Unified Firewall.
Recommendations:
1) Note the direction of the arrow when configuring NAT (only when the "Service Specific Settings" are used):
In the default configuration the option Use Connection Settings is selected. With this option NAT is used for a connection between a local network an an Internet site. Therefore no additional settings are necessary in most cases.
When using the option Use Service Specific Settings a Unified Firewall offers numerous options for NAT configuration. Most commonly, only data traffic in the direction of the Internet is masked.
The option for this is from left-to-right. Here, the arrow points from the network icon towards the Internet icon.
Using the option bidirectional also provides a functional Internet connection. However, if you operate port forwarding, the sender address displayed is that of the Unified Firewall and not that of the original sender.
The option right-to-left prevents any Internet communication, since communication from the local network to the Internet is unmasked. Only incoming communication is masked.
2) Use the “Network” object instead of the “IP range” object for the entire network:
Using an IP range means that, in the background, a specific rule is created for each IP address. This should therefore only be used for contiguous IP addresses and not for large address ranges or even an entire network.
Using a network creates a single rule only.
3) Avoid using the same protocols when cascading:
If the same protocol is allowed for a network object (in this example INTRANET) and for a downstream host object (in this example Admin PC), this leads to a twofold rule generation. This should be avoided.
An exception would be when using a proxy and exceptions are required for individual hosts (for example, if the HTTP proxy for the HTTPS protocol is used for the INTRANET network and HTTPS without an activated proxy is used on the downstream host Admin PC).
Cascading a network, an IP range and a host using the same protocol should be avoided at all costs, as otherwise this would result in the threefold generation of rules.
4) Avoid creating rules with duplicate ports/protocols:
If you operate a custom service and you add an additional service that is already a part of the custom service, this leads to a twofold rule generation. This should be avoided.
Example:
The custom service Port_Range contains the TCP and UDP ports 1–1000. The protocol HTTPS (TCP port 443) is added, even though this is already included in the service Port_Range. This leads to a twofold generation of rules.
