Side menu in new root page

I have very simple app of ionic2.

App flow is as follows:

Login Page(root) -> authenticate page-> mainPage

I have set this mainPage as my root page. I have used this.navCtrl.SetRoot(mainpage). This mainPage is now root page. it contain side menu. Now i want this side menu to appear in all pages navigated from this side menu. I mean this side menu remains same in all pages.

My main Page looks like this
Menu Content
<ion-nav #content>

Now when i use this.navCtrl.push from mainPage then this side menu is gone. It should push that page in ion-nav as per documentation.

Any help will be highly appreciated.