I want to add LTM to GTM on same box. I have gone through following link, but little confused as it says about adding GTM also. Why this is required? I mean we can simply add LTM self IP in servers, GTM addition means what exactly?
GTM doesn't really exist anymore, it is called DNS now
that link talks about a situation where you have dedicated LTM and dedicated DNS (formerly GTM) boxes, so different appliances. in that case you have to make them work together with the command listed.
but you can also just run LTM and DNS (formerly GTM) on the same box if your license allows that.