Changing camera OnEnterTrigger (in and out from same trigger)

I want to go through a trigger so when i pass it i change the camera. I can do it one way, but now I wanna do it the other way around, if i go through the same trigger change the camera to the first one.

Camera1 ----Through trigger----> Camera2 /// Camera2 ----Through trigger-----> Camera1

All in the same trigger. I also need to change the tag to MainCamera everytime i swithc cameras, so that my raycasting from camera to mouse work.
I got this at the moment:

using UnityEngine;
using System.Collections;

public class ChangeCamera : MonoBehaviour
{
    public Camera cam_1;
    public Camera cam_2;
    // Use this for initialization
    void Start ()
    {

    }
   
    // Update is called once per frame
    void Update ()
    {
       
    }

    void OnTriggerEnter ()
    {
        cam_1.enabled = !cam_1.enabled;
        cam_2.enabled = !cam_2.enabled;
    }

    void OnTriggerExit ()
    {

    }                  
}

Nevermind i got it working, The second camera have to be deactivated on the scene, now is working properly