TL;DR version: what router smarts can I add via an external box like a Raspberry/Banana Pi or equivalent?

There are a large number of threads looking for suggestions for routers to replace ISP-supplied HG659 units and/or help configuring said replacement routers. Most of these threads have at least one response pointing out that the HG659 is actually a pretty good router, at least in terms of routing performance. It also has the significant advantage (certainly from my perspective as family and friend tech support officer) of being ISP supported, including things like auto-provisioning the VOIP and remote troubleshooting.

Where the HG659 seems to fall down is (a) wifi performance; and (b) for want of a better word, "smarts".

The wifi performance may be due to unrealistic expectations. In any event, wifi performance issues will undoubtedly be best resolved by adding wifi access points. I'm a total convert to the ceiling mounted variety. For most houses, a couple of runs of ethernet from router into the roof is hands down going to provide the results from the ease/coverage/speed/neatness tradeoffs. IMHO, there's far better value to be had in spending your new router budget on wifi access points.

But now I'm wondering about whether it would be possible to give the HG659 a bit of a brain transplant. Or at least offloading some of the thinking to an external box, since I'm not planning on opening it up.

Some of the smart features I use in my current router include:

- Smart DNS (though that is becoming far less important nowadays)
- VPN (OpenVPN and Tinc)
- QOS
- Bandwidth monitoring
- Parental controls (forthcoming)
- VLAN segmentation

Others might use adblocking, TOR, torrent clients and other stuff I don't know about much less understand.

I'm wondering how many of these smart features can be implemented via an external box? Probably something like a Banana Pi since it has gigabit ethernet on board. What would be the problems/limitations of this kind of set up? I know I've had a DNSMasq server running happily on a RPi before, but it required all clients to manually specify it as the DNS server. I couldn't get my then-router to forward the RPi/DNSMasq as DNS server.

I suspect that VLAN segmentation in particular would be difficult via an external box and might require something like a managed switch to handle this.

I'm not quite sure what I really hope to achieve out of this. I like my current router with the inbuilt smarts. The query originated in one of those thoughts that pop into my head at 2am instead of sleeping and then progressed to wouldn't it be great if I could put a plug and play VPN box on my mum, brother and sister's networks for remote support, right through to how much of my current router's custom firmware goodness could I cram into such a box. In some glorious far off future I'm kind of thinking of a buy-this-$99-box, copy-this-software-onto-an-SD-card, change-a-couple-of-settings and connect-to-your-existing-ISP supported-router alternative to buying a new (unsupported) router and/or flashing custom firmware.

As an aside, it's interested to trace the trend from multiple boxes (modem, router, wireless) converging into an all-in-one (that might cost more than some PCs), and now (perhaps) splitting out again with ONTs, cable modems and WAPs.