Ionic4 ion-tab default selection

Ionic Framework
1

I am implementing ion-tabs.
One Parent Page and under it 5 tabs.
Every-time when I come on parent page I have to tap on first tab and then it get open.

I want that when I land on parent page then by default first tab should open.
How can I achieve that.

Code in ParentPage.html

<ion-content padding> 
                        <ion-tabs>

                                <ion-tab-bar slot="bottom">

                                    <ion-tab-button tab="tab1">
                                        <ion-icon name="folder"></ion-icon>
                                    </ion-tab-button>
                                    <ion-tab-button tab="tab2">
                                        <ion-icon name="folder"></ion-icon>
                                    </ion-tab-button>
                                    <ion-tab-button tab="tab3">
                                        <ion-icon name="folder"></ion-icon>
                                    </ion-tab-button>
                                    <ion-tab-button tab="tab4">
                                        <ion-icon name="folder"></ion-icon>
                                    </ion-tab-button>
                                    <ion-tab-button tab="tab5">
                                        <ion-icon name="folder"></ion-icon>
                                    </ion-tab-button>

                                </ion-tab-bar>

                            </ion-tabs>
         </ion-content>

ParentPage.Module.ts

const routes: Routes = [
    {
      path: 'tabs/:id',
      component: ParentPage,
      children:
        [
          {
            path: 'tab1',
            children:
              [
                {
                  path: '',
                  component: Tab1Component
                }
              ]
          },
          {
            path: 'tab2',
            children:
              [
                {
                    path: '',
                    component: Tab2Component                  
                }
              ]
          },
          {
            path: 'tab3',
            children:
              [
                {
                    path: '',
                    component: Tab3Component
                  
                }
              ]
          },
          {
            path: 'tab4',
            children:
              [
                {
                    path: '',
                    component: Tab4Component
                  
                }
              ]
          },
          {
            path: 'tab5',
            children:
              [
                {
                    path: '',
                    component: Tab5Component
                  
                }
              ]
          },
          {
            path: '',
            redirectTo: '/tabs/tab1',
            pathMatch: 'full'
          }
        ]
    },
    {
      path: '',
      redirectTo: '/tabs/tab1',
      pathMatch: 'full'
    }
  ];

Where I am doing mistake.

Thanks