That depends what "it" is. Routing and switching are good candidates for ASICs and simple end-host networking has good NIC offload. But Linux can be configured to perform arbitrarily complex network stuff that specialized hardware does not support.

That's about what I was going to say. Basically, you can keep adding more features to your ASIC, but the more things your ASIC supports, the more it starts to resemble a poorly-designed CPU.