diff --git a/ironic/drivers/modules/irmc/inspect.py b/ironic/drivers/modules/irmc/inspect.py
index 8eece97b85..cc192fd97e 100644
--- a/ironic/drivers/modules/irmc/inspect.py
+++ b/ironic/drivers/modules/irmc/inspect.py
@@ -99,7 +99,8 @@ def _get_mac_addresses(node):
                                   d_info['irmc_snmp_security'])
 
     node_classes = snmp_client.get_next(NODE_CLASS_OID)
-    mac_addresses = snmp_client.get_next(MAC_ADDRESS_OID)
+    mac_addresses = [':'.join(['%02x' % ord(x) for x in mac])
+                     for mac in snmp_client.get_next(MAC_ADDRESS_OID)]
 
     return [a for c, a in zip(node_classes, mac_addresses)
             if c == NODE_CLASS_OID_VALUE['primary']]
diff --git a/ironic/tests/unit/drivers/modules/irmc/test_inspect.py b/ironic/tests/unit/drivers/modules/irmc/test_inspect.py
index cf89b89e19..c74f51edb5 100644
--- a/ironic/tests/unit/drivers/modules/irmc/test_inspect.py
+++ b/ironic/tests/unit/drivers/modules/irmc/test_inspect.py
@@ -49,9 +49,9 @@ class IRMCInspectInternalMethodsTestCase(db_base.DbTestCase):
     def test__get_mac_addresses(self, snmpclient_mock):
         snmpclient_mock.return_value = mock.Mock(
             **{'get_next.side_effect': [[2, 2, 7],
-                                        ['aa:aa:aa:aa:aa:aa',
-                                         'bb:bb:bb:bb:bb:bb',
-                                         'cc:cc:cc:cc:cc:cc']]})
+                                        ['\xaa\xaa\xaa\xaa\xaa\xaa',
+                                         '\xbb\xbb\xbb\xbb\xbb\xbb',
+                                         '\xcc\xcc\xcc\xcc\xcc\xcc']]})
         inspected_macs = ['aa:aa:aa:aa:aa:aa', 'bb:bb:bb:bb:bb:bb']
         with task_manager.acquire(self.context, self.node.uuid,
                                   shared=True) as task:
diff --git a/releasenotes/notes/fix-mac-address-48060f9e2847a38c.yaml b/releasenotes/notes/fix-mac-address-48060f9e2847a38c.yaml
new file mode 100644
index 0000000000..4484598678
--- /dev/null
+++ b/releasenotes/notes/fix-mac-address-48060f9e2847a38c.yaml
@@ -0,0 +1,3 @@
+---
+fixes:
+  - This fixes InvalidMAC exception of iRMC out-of-band inspection.