diff --git a/neutron_tempest_plugin/common/utils.py b/neutron_tempest_plugin/common/utils.py
index f03762c..1526ecf 100644
--- a/neutron_tempest_plugin/common/utils.py
+++ b/neutron_tempest_plugin/common/utils.py
@@ -136,3 +136,74 @@
 def call_url_remote(ssh_client, url):
     cmd = "curl %s --retry 3 --connect-timeout 2" % url
     return ssh_client.exec_command(cmd)
+
+
+class StatefulConnection:
+    """Class to test connection that should remain opened
+
+    Can be used to perform some actions while the initiated connection
+    remain opened
+    """
+
+    def __init__(self, client_ssh, server_ssh, target_ip, target_port):
+        self.client_ssh = client_ssh
+        self.server_ssh = server_ssh
+        self.ip = target_ip
+        self.port = target_port
+        self.connection_started = False
+        self.test_attempt = 0
+
+    def __enter__(self):
+        return self
+
+    @property
+    def test_str(self):
+        return 'attempt_{}'.format(str(self.test_attempt).zfill(3))
+
+    def _start_connection(self):
+        self.server_ssh.exec_command(
+                'echo "{}" > input.txt'.format(self.test_str))
+        self.server_ssh.exec_command('tail -f input.txt | nc -lp '
+                '{} &> output.txt &'.format(self.port))
+        self.client_ssh.exec_command(
+                'echo "{}" > input.txt'.format(self.test_str))
+        self.client_ssh.exec_command('tail -f input.txt | nc {} {} &>'
+                'output.txt &'.format(self.ip, self.port))
+
+    def _test_connection(self):
+        if not self.connection_started:
+            self._start_connection()
+        else:
+            self.server_ssh.exec_command(
+                    'echo "{}" >> input.txt'.format(self.test_str))
+            self.client_ssh.exec_command(
+                    'echo "{}" >> input.txt & sleep 1'.format(self.test_str))
+        try:
+            self.server_ssh.exec_command(
+                    'grep {} output.txt'.format(self.test_str))
+            self.client_ssh.exec_command(
+                    'grep {} output.txt'.format(self.test_str))
+            if not self.should_pass:
+                return False
+            else:
+                if not self.connection_started:
+                    self.connection_started = True
+                return True
+        except exceptions.SSHExecCommandFailed:
+            if self.should_pass:
+                return False
+            else:
+                return True
+        finally:
+            self.test_attempt += 1
+
+    def test_connection(self, should_pass=True, timeout=10, sleep_timer=1):
+        self.should_pass = should_pass
+        wait_until_true(
+                self._test_connection, timeout=timeout, sleep=sleep_timer)
+
+    def __exit__(self, type, value, traceback):
+        self.server_ssh.exec_command('sudo killall nc || killall nc')
+        self.server_ssh.exec_command('sudo killall tail || killall tail')
+        self.client_ssh.exec_command('sudo killall nc || killall nc')
+        self.client_ssh.exec_command('sudo killall tail || killall tail')
diff --git a/neutron_tempest_plugin/scenario/test_security_groups.py b/neutron_tempest_plugin/scenario/test_security_groups.py
index 8b7098e..e574a1b 100644
--- a/neutron_tempest_plugin/scenario/test_security_groups.py
+++ b/neutron_tempest_plugin/scenario/test_security_groups.py
@@ -277,6 +277,50 @@
                       'remote_ip_prefix': cidr}]
         self._test_ip_prefix(rule_list, should_succeed=False)
 
+    @decorators.idempotent_id('01f0ddca-b049-47eb-befd-82acb502c9ec')
+    def test_established_tcp_session_after_re_attachinging_sg(self):
+        """Test existing connection remain open after sg has been re-attached
+
+        Verifies that new packets can pass over the existing connection when
+        the security group has been removed from the server and then added
+        back
+        """
+
+        ssh_sg = self.create_security_group()
+        self.create_loginable_secgroup_rule(secgroup_id=ssh_sg['id'])
+        vm_ssh, fips, vms = self.create_vm_testing_sec_grp(
+                security_groups=[{'name': ssh_sg['name']}])
+        sg = self.create_security_group()
+        nc_rule = [{'protocol': constants.PROTO_NUM_TCP,
+                    'direction': constants.INGRESS_DIRECTION,
+                    'port_range_min': 6666,
+                    'port_range_max': 6666}]
+        self.create_secgroup_rules(nc_rule, secgroup_id=sg['id'])
+        srv_port = self.client.list_ports(network_id=self.network['id'],
+                device_id=vms[1]['server']['id'])['ports'][0]
+        srv_ip = srv_port['fixed_ips'][0]['ip_address']
+        with utils.StatefulConnection(
+                vm_ssh[0], vm_ssh[1], srv_ip, 6666) as con:
+            self.client.update_port(srv_port['id'],
+                    security_groups=[ssh_sg['id'], sg['id']])
+            con.test_connection()
+        with utils.StatefulConnection(
+                vm_ssh[0], vm_ssh[1], srv_ip, 6666) as con:
+            self.client.update_port(
+                    srv_port['id'], security_groups=[ssh_sg['id']])
+            con.test_connection(should_pass=False)
+        with utils.StatefulConnection(
+                vm_ssh[0], vm_ssh[1], srv_ip, 6666) as con:
+            self.client.update_port(srv_port['id'],
+                    security_groups=[ssh_sg['id'], sg['id']])
+            con.test_connection()
+            self.client.update_port(srv_port['id'],
+                    security_groups=[ssh_sg['id']])
+            con.test_connection(should_pass=False)
+            self.client.update_port(srv_port['id'],
+                    security_groups=[ssh_sg['id'], sg['id']])
+            con.test_connection()
+
     @decorators.idempotent_id('7ed39b86-006d-40fb-887a-ae46693dabc9')
     def test_remote_group(self):
         # create a new sec group
diff --git a/zuul.d/master_jobs.yaml b/zuul.d/master_jobs.yaml
index e9599bf..11a90b0 100644
--- a/zuul.d/master_jobs.yaml
+++ b/zuul.d/master_jobs.yaml
@@ -206,7 +206,11 @@
       network_available_features: *available_features
       # TODO(slaweq): remove trunks subport_connectivity test from blacklist
       # when bug https://bugs.launchpad.net/neutron/+bug/1838760 will be fixed
-      tempest_exclude_regex: "(^neutron_tempest_plugin.scenario.test_trunk.TrunkTest.test_subport_connectivity)"
+      # TODO(akatz): remove established tcp session verification test when the
+      # bug https://bugzilla.redhat.com/show_bug.cgi?id=1965036 will be fixed
+      tempest_exclude_regex: "\
+          (^neutron_tempest_plugin.scenario.test_trunk.TrunkTest.test_subport_connectivity)|\
+          (^neutron_tempest_plugin.scenario.test_security_groups.NetworkSecGroupTest.test_established_tcp_session_after_re_attachinging_sg)"
       devstack_localrc:
         Q_AGENT: openvswitch
         Q_ML2_TENANT_NETWORK_TYPE: vxlan