AI walk through solid walls

The AI in my FPS walk right through solid walls, I've box colliders, mesh colliders, rigid bodies but I can't get them to not walk through solid walls. Please help me out.

This is my AI script.

 var distance;
 var target : Transform;    
 var lookAtDistance = 15.0;
 var stopDistance = 3;
 var moveSpeed = 5.0;
 var damping = 6.0;
  
 var damage:float = 17;
 var range = 100.0;
 var force = 10.0;
 var muzzleFlash : Renderer;
 var muzzleLight : Light;
  
  
 var Health = 100;
 var deadReplacement : Transform;
 var dieSound : AudioClip;
  
 static var isDead = false;
  
 static var allowfire : boolean = true;
  
 function Start (){
 muzzleFlash.enabled = false;
 muzzleLight.enabled = false;
 allowfire = true;
 }
  
 function Update () {
     target = GameObject.FindWithTag("Player").transform;
     distance = Vector3.Distance(target.position, transform.position);
  
     if((distance < lookAtDistance)){
     lookAt ();
     }
     if(allowfire == true){
     fire();
 }
 }
  
  
 function lookAt (){
     var rotation = Quaternion.LookRotation(target.position - transform.position);
     transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * damping);
     transform.Translate(Vector3.forward * moveSpeed *Time.deltaTime);
     animation.Play("walk");
 }
  
 function ApplyDammage (TheDammage : int)
 {
     Health -= TheDammage;
  
     if(Health <= 0)
     {
        Dead();
     }
 }
  
 function Dead () {
     // Destroy ourselves
     Destroy(gameObject);
     Destroy(transform.parent.gameObject);
  
     // Play a dying audio clip
     if (dieSound)
     AudioSource.PlayClipAtPoint(dieSound, transform.position);
 }
  
 static function CopyTransformsRecurse (src : Transform,  dst : Transform) {
     dst.position = src.position;
     dst.rotation = src.rotation;
  
     for (var child : Transform in dst) {
        // Match the transform with the same name
        var curSrc = src.Find(child.name);
        if (curSrc)
          CopyTransformsRecurse(curSrc, child);
     }
 }
  
 function fire(){
 allowfire = false;
 audio.Play();
  
 var direction = transform.TransformDirection(Vector3.forward);
 var hit : RaycastHit;
  
 // Did we hit anything?
 if (Physics.Raycast (transform.position, direction, hit, range)) {
 Debug.DrawRay(transform.position, direction * range, Color.green);
 // Apply a force to the rigidbody we hit
 if (hit.rigidbody)
 hit.rigidbody.AddForceAtPosition(force * direction, hit.point);
 hit.collider.SendMessageUpwards("ApplyDamage", damage, SendMessageOptions.DontRequireReceiver);
 }
  
 muzzleFlash.renderer.enabled = true;
 muzzleLight.enabled = true;
 yield WaitForSeconds (0.04);
 muzzleFlash.renderer.enabled = false;
 muzzleLight.enabled = false;
  
  
 yield WaitForSeconds(0.3);
 allowfire = true;
 }
  
 function OnTriggerEnter(hit:Collider){
 if(hit.tag == "Player"){
 hit.transform.SendMessage("Damage",damage);
 }
 }