DHCP + PPPOE over 1 WAN?

Question

Mikrotik

Hello!
Faced the need for the following settings:
Available: 2 Hap AC routers, we connect via PPPOE.
As it was before: port 1-WAN, PPPOE is configured, ports 2,3,4 - LAN, port 5 goes to an IPTV set-top box, which needs to get an IP provider via DHCP in order to work (it was decided by removing the port from the bridge and setting WAN as the port master ).
As needed now: port 1-WAN, PPPOE configured, ports 2,3,4 - LAN, port 5 goes to the second router. On the second router there are 3 ports for LAN and again 1 port for the set-top box. The problem could be solved by forwarding an additional cable to the set-top box, but unfortunately this is not possible.
Advise how to be! Thanks in advance!

Answer 1

Dmitry's answer is theoretically correct. But in practice, I was faced with the fact that for some reason the prefix multicast was transferred to the internal network too. I made the VLAN settings on the switch chip - everything rustled as it should :) Now I'll try to describe it and redo it on my knee (there was 2011).
On the 1st router on ports 3-5, enable master-port=ether2, then:

/interface ethernet switch port
set ether2 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether3 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether4 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether5 default-vlan-id=1 vlan-header=add-if-missing vlan-mode=secure

/interface ethernet switch vlan
add ports=ether2,ether3,ether4,ether5,switch1-cpu switch=switch1 vlan-id=1
add ports=ether5,switch1-cpu switch=switch1 vlan-id=2

/interface vlan
add comment=local interface=ether2 name=vlan1 vlan-id=1
add comment=iptv interface=ether2 name=vlan2 vlan-id=2

/interface bridge
add comment="LAN bridge" name=bridge1
add comment="WAN bridge" name=bridge2

/interface bridge port
add bridge=bridge1 interface=vlan1
add bridge=bridge2 interface=vlan2
add bridge=bridge2 interface=ether1

On the second router on ports 2-5, enable master port = ezer1, then:

/interface vlan
add interface=ether1 name=vlan1 vlan-id=1
/interface ethernet switch port
set ether1 default-vlan-id=1 vlan-header=add-if-missing vlan-mode=secure
set ether2 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether3 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether4 default-vlan-id=1 vlan-header=always-strip vlan-mode=secure
set ether5 default-vlan-id=2 vlan-header=always-strip vlan-mode=secure
set switch1-cpu default-vlan-id=1 vlan-mode=secure

Cable from the 5th port of the first router to the 1st port of the second.
The prefix, respectively, in the 5th port of the second router ..
If I wrote something incorrectly, I apologize, because no irons to check.
Oh yes. Move the pppoe client to an external bridge.

Answer 2

I understand that you have at least one cable between the routers?
Then you can try to take an Ethernet splitter, which "crams" two 100 megabit connections into one wire.
On this one wire, you will also have the set-top box connected directly to the first router and the second router to where you want.
PS. The splitter is passive and inexpensive.

Answer 3

If I correctly understood the essence of the task, then you can do this:
On port 5 of the first router, we make 2 VLANs - one is bridged with WAN, the second with LAN.
On the second router, we catch 2 VLANs - one is bridged with a local network, the second - with a set-top box port.
And you don’t have to make anything on the physical level.