I would like your feedback if this is possible with RouterOS on a RB600 (as an example)

To start with I have 16 users at the work location.

Then i have 4 PPPoE accounts for internet access from the provider.

What i want is to create 4 subnets each allowing ONLY 4 (ips) users. so i figured i'd use the /29 network bit.
192.168.1.x/29
192.168.2.x/29
192.168.3.x/29
and
192.168.4.x/29.
this should allow me enough IPs in the /29 network.

Now, when a new user joins he randomly pulls an ip from lets 192.168.1.x/29 until that fills up then the router should give IPs from the next subnet 192.168.2.x/29 and so on.

The most imporatnt part here thats required is each subnet has to have its own PPPoE dialout client login and work on that with its own route and so on.
so for
192.168.1.x/29 we give pppoeDial1 and it has to use that.
192.168.2.x/29 we give pppoeDial2 and it has to use that.
and so on

we dont want a user from 192.168.2.x to be using the internet from 192.168.1.x.

is this workable?

Sure.

For DHCP just set several dhcp pools and set them in chain ' when one is used up it will switch to next.

To route specific users to specific pppoe interface you have to use mark routing. It's pretty much basic setup that you may learn form manual.

In principle, you use mangle to set routing mark for selected ip's or ip range and then in routing set default gateway route for that mark to route traffic through wanted pppoe interface.

Sure.

For DHCP just set several dhcp pools and set them in chain ' when one is used up it will switch to next.

To route specific users to specific pppoe interface you have to use mark routing. It's pretty much basic setup that you may learn form manual.

In principle, you use mangle to set routing mark for selected ip's or ip range and then in routing set default gateway route for that mark to route traffic through wanted pppoe interface.

wonderful.

Would you be so kind as to provide me with a working example for one of the subnets and i can fill in the rest ?
(i am still a beginner no matter how much i like to think i know about routerOS)

can anyone help me with the mangle rules, please?

anybody want to help with this please?

You could mark the routing based on a src address range - i.e. create a mangle rule on the prerouting chain set the src address to 192.168.1.x-192.168.1. and set action to Mark Routing and set a routing mark such as PPPoE1.

If the PPPoE connections get static IPs you could create the routing entries manually and mark them with the appropriate routing marks. If the PPPoE connections get dynamic IPs/gateways etc. then in IP/Routes create 4 VRFs with the same names as you picked for the routing marks and assign one PPPoE interface to each VRF and flag the PPPoE connections to create default routes. That *should* create routing table entries with the appropriate routing marks but do check - it works for DHCP clients but I think there are some bugs in the VRF support still....