fix for #61;

README.md

@@ -11,7 +11,7 @@ You can use older Netbox version with 0.3.9 version of this plugin.
 The plugin is available as a Python package in pypi and can be installed with pip  
 For NetBox 2.10 or 2.11: 
 ```
-pip install netbox-bgp=0.3.9
+pip install netbox-bgp==0.3.9
 ```
 For NetBox 3.0: 
 ```

netbox_bgp/api/serializers.py

@@ -161,6 +161,21 @@ class BGPSessionSerializer(TaggedObjectSerializer, CustomFieldModelSerializer):
     class Meta:
         model = BGPSession
         fields = '__all__'
+        validators = []
+
+    def validate(self, attrs):
+        qs = BGPSession.objects.filter(
+            device=attrs.get('device'),
+            local_as=attrs.get('local_as'),
+            local_address=attrs.get('local_address'),
+            remote_as=attrs.get('remote_as'),
+            remote_address=attrs.get('remote_address'),
+        )
+        if qs.exists():
+            raise ValidationError(
+                {'error': 'BGP Session with this Device, Local address, Local AS, Remote address and Remote AS already exists.'}
+            )
+        return attrs
 
     def to_representation(self, instance):
         ret = super().to_representation(instance)