Connecting to tunnelbroker.net from dynamic public ip address requires the address to be sent to the remote, and to be set locally. This script does both.
Just install the script:
Installing ppp-on-up makes this script run when ever a ppp connection is established.
The configuration goes to interface's comment:
/ interface 6to4 set comment="tunnelbroker, user=user, pass=s3cr3t, id=12345" tunnelbroker;
Also enabling dynamic DNS in Mikrotik cloud is required:
/ ip cloud set ddns-enabled=yes;