I've been using Softether for a very long time, and it contains a feature to connect to the router via VPN even if it's located behind NAT. It's called VPN Azure. You register a free domain email@example.com and just connect to that.
The softether package is still 5MB and since I'm trying to fit a lot of functionality into a tiny 16MB flash I'm wondering. What's the smallest package that has a similar feature?
And, no I don't really want to rely on using my own public IP server somewhere else to bounce off of. It's hard to ensure that will always be online.
I have heard of other free services but I forgot their names.
This is not to be used as the main form of access but as a backdoor in case the main access goes down because I configured it wrong or something.