Actually re-reading the rules for internal router it seem as if the internal router does not have to be wireless enabled after all. Sorry for the confusion. Parts of 5th edition ruleset seem to have slipped my mind lately

Devices in SR5 dynamically self-organize, self-configure and automatically connect to other devices in their vicinity (Google
Mesh Networking to get an idea of a 2020 technology that have similar traits). This give individual devices a huge boost in efficiency and performance (Google
Distributed Computing to get an idea of a 2020 technology that have similar traits) and this in turn is one of the reasons why you are granted a wireless bonus when your device is wireless enabled and connected to other wireless enabled devices in its vicinity. With an Internal Router you get this benefit by connecting all your augmentations via your nervous system into an internal meshnet of sorts, without actually exposing your augmentations to devices outside your body or the matrix as a whole. This give your reaction enhancers and wireless reflexes the computing power and the increased performance to break the +4 augmentation limit, even though they are not wireless enabled and even though they are not exposed to the matrix as a whole.
CF p. 84 Internal Router
Using the body’s internal neural network as “wires,” the internal router allows the user’s cybernetics to communicate with one another as if they were wirelessly connectedThen you have augmentations that might need to connect to an external device of sorts (like your smarteyes that need to connect to your wireless enabled smartgun). With a wireless enabled datajack (or wireless enabled internal commlink, wireless enabled internal cyberdeck or perhaps a wireless enabled control rig) this can be made possible while your other augmentations are wireless disabled (if you have an internal router that is). For example, if you have a wireless enabled smartgun, an internal router (which can be wireless disabled, I said something else a few posts above - sorry) and a wireless enabled datajack then you get to establish a wireless smartgun system connection even if your smarteyes are wireless disabled (this will obviously stop working if someone brick your wireless enabled datajack or your wireless enabled smartgun, but at least your internal router, your smarteyes, your reflex enhancers and your wired reflexes are 'safe').
CF p. 84 Internal Router
...and, if expanded via a datajack or similar broadcast-enabled piece of cyberware, with the rest of the user’s gear.
This allows the use of some wireless functionality, such as the quick-loading function of a smartgun or the engagement of a smuggling compartmentA third reason why your devices tend to give you a wireless bonus is because they also, in addition to increased computing power and performance, get to access various matrix resources (like skillwires if you have a wireless skillsoft subscription). This is, however, not something that internal router will help out with (your skillwires still have to be wireless enabled if you wish to make use of your wireless skillsoft subscription - having an internal router does not change this fact).
CF p. 84 Internal Router
...but not those that require an outside network or similar function, such as skillwire downloads.