On the contrary, Stateful Firewalls filter packets by matching to valid states in the state table. Stateless Firewall filters based on header information in a packet like Source IP, Destination IP, port number etc. In fact, Stateful Firewalls use the concept of a state table where it Stores the state of legitimate connections. In Stateful vs Stateless Firewall, Stateless Firewall works by treating each packet as an isolated unit, Stateful firewalls work by maintaining context about active sessions and use “state information” to speed packet processing. All new traffic trying to reach the client application will be dropped by the stateful firewall.Stateless and Stateful Firewalls are 2 commonly referred to as Firewall types. The connection tracker on the stateful firewall will only allow incoming packets which are related to communications started by the internal clients. Client side firewall: A client program which strictly connect to a small set of trusted hosts (internal) can be protected using stateless firewalls with specific rules.Ī stateful firewall on the other hand can be used to protect client applications which connect to a large number of untrusted hosts (webservers on internet, peer-to-peer traffic).As the server ports are well known to the firewall and the server expects new connection anyway, stateless firewalls can handle this use case. In this case firewall can be explicitly programmed to allow connection to and from the server port. Server side firewall: If you are running a purely server application with well-known ports on a machine.When to use Stateless firewall?Ī stateless firewall can be a faster and less resource intensive alternative in the following cases Thus, the resources needed by such a filtering process is much less. In case of stateful firewall the connection state must be synchronized across multiple firewalls to provide a consistent view of active connections.Ī stateless firewall on the other hand deals with a single packet at a time. This requires a lot of resources (memory, cpu) on the firewall and as such is a costly.Īnother consideration is load balancing traffic on multiple firewalls. New connections are actively added and expired connection are purged from the connection state maintained by the firewall. It needs to maintain the state of all the active connection. Stateful firewall needs to track each of the connection that passes though the firewall. Stateless firewall on the other hand does not have any knowledge of what connections the client has initiated, instead it depends purely on the attributes of the packet like source, destination address etc. Also, note that this makes it possible to write generic rules for a stateful firewall. ![]() Stateless Firewall configuration: Allow traffic going out to port 80 on Allow traffic coming from host and port 80įrom the above it is clear that the stateful firewall will allow incoming traffic only if it is related to connections the client has started. Stateful Firewall configuration: # Generic rule to allow clients to connect to anyĪllow traffic related to connections initiated by any internal client back to the same clientĭeny any other traffic coming in to the client Let’s see what configuration of the stateful and stateless firewall are needed to make this communication work. Let’s take a scenario to understand this betterĪ client sitting behind firewall connects to a web server and receives a reply. If a packet belongs to an already running flow it can be allowed, while a new connection form the untrusted host can be dropped. A stateful firewall can detect these states. A TCP connection for example goes through the handshake (SYN-SYN+ACK-ACK), to EASTABLISHED state, and finally is CLOSED. ![]() A firewall can be stateful or statelessĪ stateful firewall is capable of tracking connection states, it is better equipped to allow or deny traffic based on such knowledge. Firewalls provide traffic filtering and protects the trusted environment for the untrusted.
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