By contrast, on modern Enterprise-grade devices, these rules are often installed into the router’s dedicated forwarding hardware. On cheaper or older devices, these stateless filters require traffic to be processed by the main CPU of the router, which can be quite intensive. Most routers offer some kind of stateless filter. Nor do these rules keep track of flows, or look for any known threats or attacks in the packet, as part of a wider flow. These rules tend to match only on things in the header – in other words, they don’t look deep into the payload of the packet to see if the application is the same as what the TCP/UDP port claims it is. In particular, the “stateless” part means that your network device looks at each packet or frame individually. This is a set of rules that you generally apply to an interface, to control traffic coming in or going out of it. There are two categories of filtering rule that you can create.
There are tons of resources online that go into much more detail about the difference between the two, and you should definitely have a Google search for a more thorough definition.įor the time being, the text below should be enough to get you started. This post is a super-quick description of the definition, just so you can follow along with my Beginners Guide to Junos Firewall Filters post. Regardless of the name, there is a difference between a “stateful rule” and a “stateless rule”. Always great to have to remember five words for the same thing! Different vendors have different names for the concept, which is of course excellent. These rules may be called firewall filters, security policies, access lists, or something else.
Routers, switches, and firewalls often come with some way of creating rules that flows through them, and perhaps to even manipulate that traffic somehow.
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