![]() ![]() Also can operate at Layer 3 and higher in the OSI reference model. ■ TCP synchronization information Application Layer Gateway (Proxy Firewall)Īpplication layer firewalls, which are also sometimes called proxy firewalls or application gateways. ![]() An extended ACL on a Cisco router can use many matching criteria against the Layer 3 and Layer 4 headers, including the following: As soon as a match occurs, the ACL stops processing the rest of the list and implements the action against the packet, which is either a permit or deny. Some applications jump around and use many ports, some of which are dynamic.īecause packet filtering uses a simple rule set (a packet that comes in or out of an interface where there is an ACL applied for filtering), there is a check against the packet with the entries in the ACL from top to bottom.Stateless: does not maintain a seession information for current flows of traffic going through the router.Extremely long ACLs are difficult to maintain. ![]() Does not filter fragmented packets with the same accuracy as nonfragmented packets.Can perform many of the basic filtering needs without requiring the expense of a high-end firewall.Are a minimal impact on network performance.Have minimal impact on network performance.Based on Simple sets of permit or deny entries.Needs to be allowed through the firewall, which can be tricky if you have many users that need to access many servers. One of the challenges with static packet filtering is that the administrator must know exactly what traffic An example of a firewall technology that uses static packet filtering is a router with an ACL applied to one or more of its interfaces for the purpose of permitting or denying specific traffic. Static packet filtering is based on Layer 3 and Layer 4 of the OSI model. Static Packet Filtering (stateless Firewall) ![]()
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