Talk:Bridge Mode (fibr)/@comment-112.204.227.151-20190526114414/@comment-1155842-20190526150750

Using your custom static IP address for the ONU should be fine as long as no connections are established yet. Once it completes its handshake with the facilities, it takes on the assigned WAN IP address and you need a special method to access the ONU gateway while an active connection is established. This is why fiber optic cables are removed when configuring the ONU.

In a nutshell:

192.168.5.21 is accessible while no connection is established.