Recently, uncle has been here and there helping co-workers (DIGI & Umobile) on enabling VoLTE.
For DIGI case, need to livechat with their agents and request them to enable VoLTE before Wifi Calling can be used. No luck on Umobile if phone is unsupported.

However, the signal strength inside the building is very low and most fallback to 2G/3G.
Since the office has wifi (fiber backend), uncle plans enable WiFi calling for them.
Unfortunately, when uncle enabled Wifi Calling and select it to be preferred option, it doesn't work.

Uncle logged into the router (Hmm, TP-Link router at workplace. ) and found out "IPSec Passthrough" at Application Layer Gateway (ALG, at the NAT Forwarding section) is disabled.
Once IPSec Passthrough is enabled, everyone phone VoWIFI (Digi & Umobile) logo popped up and it works.

Seem like it is their first time seeing that VoWIFI logo, I asked them if it ever work with the their wifi back at home.
To my surprise, they replied it never work.

Thus, for the next 11 co-workers, I logged into their home TP-Link router remotely (thanks teamviewer, they are unifi subscribers with C1200 router) and discovered IPSec Passthrough is disabled by default.

A simple checkbox and save, voila. VoWIFI works.


Hopefully, this simple advice can help those who never got their Wifi Calling work.

Wonder if IPSec is disable or enabled by default for Asus, DLink or any other brand router?

Good to know that.

Yup, I just ask them to use airplane mode and enable wifi only since switching between 4G to 3G/2G drains a lot of battery power.

Probably.





Anyone using the ancient cylinder D-Link can verify this IPSec Passthrough too?

TP-LINK programmers definitely don't have any common sense and I can be certain of their stupidity and ignorance of user complaints.