diff --git a/tempest/api/network/test_security_groups.py b/tempest/api/network/test_security_groups.py
index 97ccee9..24bd8ea 100644
--- a/tempest/api/network/test_security_groups.py
+++ b/tempest/api/network/test_security_groups.py
@@ -23,7 +23,6 @@
 
 
 class SecGroupTest(base.BaseSecGroupTest):
-    _project_network_cidr = CONF.network.project_network_cidr
 
     @classmethod
     def skip_checks(cls):
@@ -209,7 +208,7 @@
         protocol = 'tcp'
         port_range_min = 76
         port_range_max = 77
-        ip_prefix = self._project_network_cidr
+        ip_prefix = str(self.cidr)
         self._create_verify_security_group_rule(sg_id, direction,
                                                 self.ethertype, protocol,
                                                 port_range_min,
@@ -238,4 +237,3 @@
 
 class SecGroupIPv6Test(SecGroupTest):
     _ip_version = 6
-    _project_network_cidr = CONF.network.project_network_v6_cidr
diff --git a/tempest/api/network/test_security_groups_negative.py b/tempest/api/network/test_security_groups_negative.py
index 435673b..d054865 100644
--- a/tempest/api/network/test_security_groups_negative.py
+++ b/tempest/api/network/test_security_groups_negative.py
@@ -24,7 +24,6 @@
 
 
 class NegativeSecGroupTest(base.BaseSecGroupTest):
-    _project_network_cidr = CONF.network.project_network_cidr
 
     @classmethod
     def skip_checks(cls):
@@ -110,7 +109,7 @@
         sg2_body, _ = self._create_security_group()
 
         # Create rule specifying both remote_ip_prefix and remote_group_id
-        prefix = self._project_network_cidr
+        prefix = str(self.cidr)
         self.assertRaises(
             lib_exc.BadRequest,
             self.security_group_rules_client.create_security_group_rule,
@@ -225,7 +224,6 @@
 
 class NegativeSecGroupIPv6Test(NegativeSecGroupTest):
     _ip_version = 6
-    _project_network_cidr = CONF.network.project_network_v6_cidr
 
     @decorators.attr(type=['negative'])
     @decorators.idempotent_id('7607439c-af73-499e-bf64-f687fd12a842')