BGW320-500 Bridge Mode and/or IP Passthrough Question

As many as 32, yes.  See the following article:

https://www.lightwaveonline.com/fttx/article/16670533/gpon-at-full-speed-for-fttp#:~:text=GPON%20offers%20maximum%20flexibility%20because,times%20to%20keep%20costs%20down.&text=These%20buildings%20can%20be%20accessed,such%20as%20VDSL2%20and%20Ethernet.

So is that the difference between business/commercial internet service and residential: a dedicated pipe vs a shared?

Not entirely, but that's part of it.  The Support and SLAs are different.  It's like the difference between a mass produced car and a custom built one.

Got it, and again, thank you for knowledge sharing.

So, when I do a speed test, I often get 950 mbps up/down, and sometimes is half of that, say 300 or 400+ up/down. Is that drip simply network congestion?—eg my neighborhood’s usage going up? (Double checking my understanding)

@JefferMC A final question, if I may.  (This may require a separate thread, but I am posting it here as I think it is related).  This is regarding a static IP:

My understanding was that a static IP is a single IP address that you are granted (or assigned) that doesn't change.  This then allows for other clients/services to always contact whatever you are hosting at that IP address.  (My specific use case is an IP linked UHF radio repeater).

When I got my static IP address fulfilled by AT&T, what they gave me was something else.  They gave me a screenshot with the following info (I am omitting the actual numbers for privacy reasons, replaced by 'x'):

ASSIGNED STATIC IP BLOCK:

-Subnet Mask:  xxx.xxx.xxx.xxx

-Network Base Address:    xxx.xxx.xxx.xxx

-Router:    xxx.xxx.xxx.xxx

-Usable Range:    xxx.xxx.xxx.xx1 -   xxx.xxx.xxx.xx5

-Broadcast:    xxx.xxx.xxx.xxx

-IP Block Size:  5 usable, 8 total

AT&T DNS SERVERS:

-Primary DNS Server:    xx.xx.xxx.x

-Secondary DNS Server:    xx.xx.xxx.x

What do these things mean?  Or, do I ignore all but one of the IP addresses?

Many thanks again,

Mark

You have been assigned a total of 9 IP addresses.  The dynamic one (your Gateway will show it as its public IP), and a block of 8 adjacent IP addresses, of which only 5 are usable.  The Subnet Mask for your block will be 255.255.255.248 (that's 32 bits with the first 29 bit set and the last 3 clear, indicating a /29 block or 8 addresses total).  The first address is the Network base address, which is evenly divisible by 8.  This is not usable, but is what you fill in for the "Network Address" when setting up your Cascaded router.  The next 5 addresses are considered usable and you can assign anyone of them to your device(s) behind your UDMP.  The seventh one is the router address for the subnet, which the Gateway would normally assign on its LAN interface to be used as the default gateway, but I think in this case you actually want to assign as the LAN of the UDMP. The final one is the broadcast address for the subnet.

The two DNS servers IPs are the addresses that AT&T thinks you should use for your DNS servers.  They typically would be the same two your Gateway has been assigned automatically by DHCP.

@JefferMC I'm ready to go through your cascaded router process and set it up.  In my gateway's setup menu, when I go to Home Network -> Subnets & DHCP, I see the 4x options under Cascaded Router, but they're greyed out.  The first option is Cascaded Router Enable and its currently set to OFF.  I cannot click on it to turn it on.  Any ideas?  Thank you

Yes, the first step is to set that to On, then the other fields will be enabled.

I get that, but I cannot turn it on.  The box is greyed out.  I cannot change anything under cascaded router, including the off/on button

Here is what I see