No Back option in tabs page ionic2

Question

In Tabs navigation page, I couldn't find any back option in ionic2. while using hardware back button the app exits. i have put my code snippets below, any suggestion would be great.

tabs-navigation.html

 <ion-tabs >
<ion-tab [root]="tab1Root" tabTitle="Feed" tabIcon="browsers"></ion-tab>
<ion-tab [root]= "tab3Root" tabTitle="Settings" tabIcon="settings"></ion-tab>
</ion-tabs>    

tabs.navigation.ts

import {Component} from '@angular/core';
import {Events , App} from "ionic-angular";
import {BrowserPage} from '../browser/browser';
import {SettingsPage} from '../settings/settings';

@Component({
selector: 'tabs-navigation-page',
templateUrl: 'tabs-navigation.html'
})

export class TabsNavigationPage{
    tab1Root: any;
    tab2Root: any;

constructor(public events: Events , public app: App) {
    this.tab1Root = BrowserPage;
    this.tab2Root = SettingsPage;
}

}