Router at address other than 0.

You need an IP Interface which generally is less expensive than an IP Router. I suppose if an IP router had a parameter to turn off routing then it might be possible but that would be subject to KNX Standard specs and manufacturer co-operation.

We used to use IP interfaces, the control system interface changed and requires an IP Router.

Helpfully explained here.

https://ivoryegg.co.nz/product_guides/connecting-knx-and-control-4-with-ip-routers-best-practice-recommendation-from-ivory-egg

A router at a 0 address isn't an issue for new system, however it's a big issue when integrating with existing systems.

An option to acknowledge the restriction and set any address would be very useful.

Amusingly, I wrote the article you’ve referred to.

I think you have misinterpreted the correct procedure. The C4 Routing Gateway allows the C4 controller to act as a KNX IP device, having an address in the KNX topology “above” the IP Router.

Please watch the YouTube video linked in the article which may explain it in more detail.

In summary, yes, you need an IP router, and as with all IP routers it will have a last address number of “.0”.

Hi Stephen, thanks for the excellent article. I'm relieved you're not named as the author, that would have made me seem very dumb!

I haven't misunderstood the correct procedure, I just want to bend the rules with an understanding of the pros/cons.

ETS5 had a bug/feature that allowed a router at a non 0 address. This allow integration with an older KNX system with network cabling limitations and older devices that while fully working are challenging to reconfigure due to old .NET and other plugin requirements.

I accept that this isn't architecturally correct, however it's a practical, functional and pragmatic solution to add value to an existing install and offer a cost effective upgrade solution. These are typically small systems with couplers that are already configured to forward all. We seem to be doing 3/4 or these a year. Additional network cables to fix the architecture and move the router position can be added during future renovation/decorating work.

Many thanks for your responses, they are valued and I'm not deliberately trying to be argumentative.

Without specific information it’s hard to give you the most accurate advice. However, if you have line couplers with addresses 1.1.0 , 1.2.0, 1.3.0 etc there is necessarily a TP Main Line 1.0 which sits above the sub-lines.
You can install an IP router at address 1.0.0 and add a C4 controller with address 0.0.200 (or whatever) in ETS as a dummy device and in Composer using the KNX Routing Gateway with the same KNX address set.