How to connect SFP ONU stick to the router

Hi, I’m waiting now for my SFP module ( DFP-34X-2C2). I want to replace my ISP’s ONU with it. And I have one small question about it.

I have BPI-R3 router, which has two SFP cages on it. Now it is connected to separate ONU device (EP8100 model) via WAN port.
It is really simple to have internet connection now. All, that I must do - just change MAC-address of this device:

As I understand, br-wan is a bridge device, which "containing" two physical devices: wan (which is WAN port on the router) and eth1 (which is SFP port):

After changing MAC-address of br-wan device, my router get IP from ISP and have internet connection:

How can I properly swap separate ISP's ONU to SFP ONU stick? Obviously, I know, that I must copy all settings from ISP’s ONU to SFP stick (serial number, ploam password etc). I want to know how to make this module visible to me. As I understand, I must change router’s ip to something different, than 192.168.1.1 first (it is default lan ip of sfp stick). But how should I proceed after that?
Should I just add new interface with single eth1 device and give to this interface 192.168.1.2 ip address?

I don't see any reason for a wan bridge, you just configure the sfp (eth1) to be the option device 'eth1' for your (non-bridge-) wan interface - yes, naming wise it gets a little messy with wan being eth1, while the physical wan-port on the switch gets freed for other uses (be it part of br-lan, laying dormant or being used for yet another subnet/ VLAN).

Compare it to e.g. the bthub5a, which was in a roughly similar situation - your wan interface could either be the integrated dsl modem or the red (x)wan ethernet port on the switch, your choice to define in the config (/etc/config/network, option device ...).

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So, as I understand:

  1. Change router's ip adress (lan) to something different, than 192.168.1.1 (maybe 192.168.0.1)
  2. Change device in WAN interface from br-wan to eth1. Copy MAC address from br-wan device to eth1 device.

And my SFP module will be reachable on 192.168.1.1? I just don't understand how can I connect to SFP module with IP address 192.168.1.1 from my laptop, for example, which will have IP address 192.168.0.x it this case.

Not really.
There just is a distinction between the logical wan interface (with the wan firewall zone) and the switch port called wan.

The sfp/ eth1 shouldn't really have a 192.168.x.y address, I would expect it to either get a public or cgNAT IP/ IPv6 by your ISP via DHCP - or none at all, with PPPoE as protocol on top. But this depends on the ISP and their requirements. Therefore I don't see a reason why you would have to renumber your br-lan, there shouldn't be a conflict (yes, avoiding 192.168.0.x and 192.168.1.x is a sensible policy decision, but orthogonal to this).

Yes, eth1 might need to inherit (clone) the MAC address you're currently using on the wan-port.

(how to configure the sfp ONT is another question, this depends entirely on how the ONT manufacturer has designed their firmware, might be a parallel webinterface, might be custom i2c based communication. This is not dissimilar to a dsl modem again, those don't need to have a webinterface either (early ones didn't, later ones do), nor do you really need to access it after the configuration of the physical parameters of the line - but you can configure an alias (modem-)interface for its webinterface.)

It's easier to discuss the details based on your current /etc/config/network.

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