Issues with inform address
SWITCH: 192.168.1.89 b4:fb:e4:c9:06:be # Login and run: set-inform http://192.168.1.24:8080/inform
IPv6 PD issues
There are well-documented problems with the way Prefix Delegation behaves with ISPs that do/don't support a certain option, Internode in particular does seem to crop up a fair bit.
Symptoms: USG CPU usage is pegged at ~50% when IPv6 and Prefix Delegation is in use, the PD client perl script keeps crashing/restarting in a tight loop.
Cause: The client sends/requests IA_NA, and the ISP doesn't support it, so it bombs out.
Fix: A Unifi CLI setting can be done on the USG that reconfigures the client to not request IA_NA, thus avoiding this problem until it's rebooted/reprovisioned. The permanent fix is to make a json config file on the controller, which is provisioned to the USG.
Diagnosis and solutions are documented here:
In Unifi's internal config tree representation, we're looking at: show interfaces ethernet eth0 pppoe 0 dhcpv6-pd prefix-only
Guidance on doing the advanced json config is here: https://help.ui.com/hc/en-us/articles/215458888-UniFi-USG-Advanced-Configuration
# /var/lib/unifi/sites/default/config.gateway.json
{
"interfaces": {
"ethernet": {
"eth0": {
"pppoe": {
"0": {
"dhcpv6-pd": {
"prefix-only": "''"
}
}
}
}
}
}
}This change will update the provisioned config on the USG here: /var/run/dhcp6c-pppoe0-pd.conf
Once this is done, USG CPU usage should drop to pretty much zero.
More about what's going on: here's what Internode says about their IPv6 setup:
Here's what you get when your connection is set up for IPv6: Your existing IPv4 address (if static) and any existing framed route(s). A dual-stack IPv4/IPv6 PPP session. A dynamic /64 IPv6 prefix for your PPP session. A static /56 IPv6 prefix for your LAN (if you are using a router with Prefix Delegation).
The two endpoints we need to care about are the ends of the PPP session (technically PPPoE). I think our end gets an IPv6 address as a result of the PPP negotiation, but other functionality is added by using DHCPv6 to configure more client-side stuff, like DNS resolvers and stuff. One of those is getting a delegated prefix to serve up with radvd, and another option looks to be IA_NA, by which our side can get an IPv6 address for itself.
But we don't need that, because we already have a local-end (ie. the router and PPPoE client) address thanks to the PPP negotiation, as Internode promised (a dynamic /64 prefix for your PPP session).
By setting prefix-only in the Unifi config, we don't ask for IA_NA, and we just ask for prefix delegation, which is all we need.
PPPoE logging
It is pretty much non-existent, sadyly. 
General log viewing: https://help.ui.com/hc/en-us/articles/204959834-UniFi-How-to-View-Log-Files#3
I went ahead and raised the global log level as suggested here, it kinda helps now: https://community.ui.com/questions/ppp-logging/d81578bc-c34d-4a01-931e-2c52a7354480
set system syslog global facility all level debug
It comes through as pppd messages in syslog, this kinda works to read it on the USG: show log | egrep -v 'WAN_IN|sudo:|mcad:'| less