update Sliver admin
diff --git a/plstackapi/core/models/subnet.py b/plstackapi/core/models/subnet.py
index ae25b63..93a7ba5 100644
--- a/plstackapi/core/models/subnet.py
+++ b/plstackapi/core/models/subnet.py
@@ -8,7 +8,7 @@
 # Create your models here.
 
 class Subnet(PlCoreBase):
-    subnet_id = models.CharField(max_length=256, unique=True, blank=True)
+    subnet_id = models.CharField(max_length=256, unique=True)
     cidr = models.CharField(max_length=20)
     ip_version = models.IntegerField()
     start = models.IPAddressField()