A firewall generally works at layer 3 and 4 of the OSI model. Layer 3 is the Network Layer where IP works and Layer 4 is the Transport Layer, where TCP and UDP function. Many firewalls today have advanced up the OSI layers and can even understand Layer 7 – the Application Layer.

inbound outbound

# 防火墙服务

checkpoint https://www.checkpoint.com/videos/ https://sc1.checkpoint.com/documents/R81.10/WebAdminGuides/EN/CP_R81.10_HarmonyEndpointWebManagement_AdminGuide/Topics-Common-for-HEP/Configuring-Inbound-Outbound-Rules.htm?TocPath=Configuring%20Endpoint%20Policy%7CConfiguring%20Firewall%20Policy%7C_____1