"Box A" is an ONT or optical network terminal, which is really just a media converter with some additional intelligence related to how GPON schedules use of the media. It's more or less the same thing as an ADSL modem (actual modem only) except that GPON usually uses Ethernet while ADSL usually uses ATM. But both are used the other way sometimes.

For "Box B" you can use anything you wish as long as it supports PPPoE. Contact CenturyLink by phone or chat to tell them you need your PPP credentials, they'll have no trouble giving them to you. The only trick besides PPP is that CenturyLink usually uses a VLAN for customer equipment on their GPON, but that's pretty common with ethernet over ADSL as well so routers made for use with a DSL modem should have it in their UIs alongside the PPP info. Unfortunately most newer routers are made without this use case in mind so there may not be support, in which case you can always upgrade to something a little more configurable or use a computer as a router. You can ask the CSR for the VLAN ID but in every case I've seen it's 201.

I've done this a number of times and never had the CSR give me any trouble. They also don't seem to keep very good track of who has CL-owned CPE, I've ended up with "free" CenturyLink routers a couple of times because they fell through the cracks when switching to my own.

> PPoE with my credentials which were somehow hardwired because no one ever told me my username/password

They make it very hard to use your own "Box B", but I've set this up twice now (most recently last week). Get the username and password from CenturyLink (the tech that installs the service has this, or call them). Then, google search "century link vlan 201 wan tag". The trick is you need a router that has this functionality, most basic consumer ones don't.

Unfortunately, even if you follow all directions and it still doesn't work troubleshooting is a nightmare, very little or no help from their customer support.

Be aware that for many cheap routers you can't do the VLAN tagging the "normal" way via the web interface. Like this: https://blog.mapstrata.com/post/internode_openwrt/

For people with cheap/crappy hardware like me, if you have to set VLAN2 via the sub-interface then your config needs to look like this:

  config interface 'wan'
    option ifname 'eth1.2'
    option proto 'pppoe'
    option username 'your_internode_username@internode.on.net'
    option password 'SecretPassword'

All of the above can be set via the GUI, except the "eth1.2" part. The above works if you happen to be with Internode.

Ah I see. My WRT1900AC doesn't have that option. I was running OpenWRT but ran into some issues and panicked back to the default firmware. Now that I have another wireless router I might dare it again.

OpenWRT is fantastic when you get used to it. I prefer the CLI but the GUI works well too.

B probably exists so they can split fiber between multiple end users or support things like phone service over the same link. Did you use the same VPI and VCI? PPPoE also sends an identifier (the "Host-Uniq" tag if I'm understanding it right) that probably has to match what your ISP is expecting or has assigned.

I had CL fiber. VLAN tagging; The vlan tagging value was so high, OpenWRT didn't support it so I was left with the useless middle box. Your mileage may very.

OpenWRT does support VLAN tagging, it's Linux. Maybe it's a hardware support issue.

I was just about to re-install OpenWRT, but I guess I won't now.