Hi,
I saw in the changelog that advertising support was added in 2.9, I have 2.9rc5 running but I cant find it in telnet or winbox.
Is this an enabled feature yet?
It is not documented yet. But it is available under hotspot user profiles.
Just set:
/ip hotspot user profile set default transparent-proxy=yes advertise=yes
With default advertisement settings MikroTik will be advertised 
By the way, advertise-timeout means - how much time user is allowed to use
internet, after advertisement is sheduled, but is not seen yet (first http
request with html content will show advertisement).
Fine. But how to use transparent proxy with multiple gateways? 
Still doesn’t working…
kj