diff --git a/NetworkPkg/IScsiDxe/IScsiConfig.c b/NetworkPkg/IScsiDxe/IScsiConfig.c
index a588403017..498221a339 100644
--- a/NetworkPkg/IScsiDxe/IScsiConfig.c
+++ b/NetworkPkg/IScsiDxe/IScsiConfig.c
@@ -205,11 +205,11 @@ IScsiParseIsIdFromString (
 
   IsIdStr = (CHAR16 *) String;
 
-  if (StrLen (IsIdStr) != 6) {
+  if (StrLen (IsIdStr) != 6 && StrLen (IsIdStr) != 12) {
     UnicodeSPrint (
       PortString,
       (UINTN) ISCSI_NAME_IFR_MAX_SIZE,
-      L"Error! Input is incorrect, please input 6 hex numbers!\n"
+      L"Error! Only last 3 bytes are configurable, please input 6 hex numbers for last 3 bytes only or 12 hex numbers for full SSID!\n"
       );
 
     CreatePopUp (
@@ -222,6 +222,10 @@ IScsiParseIsIdFromString (
     return EFI_INVALID_PARAMETER;
   }
 
+  if (StrLen (IsIdStr) == 12) {
+    IsIdStr += 6;
+  }
+
   for (Index = 3; Index < 6; Index++) {
     CopyMem (TempStr, IsIdStr, sizeof (TempStr));
     TempStr[2] = L'\0';
diff --git a/NetworkPkg/IScsiDxe/IScsiConfigStrings.uni b/NetworkPkg/IScsiDxe/IScsiConfigStrings.uni
index 79522583de..10583f8f3b 100644
--- a/NetworkPkg/IScsiDxe/IScsiConfigStrings.uni
+++ b/NetworkPkg/IScsiDxe/IScsiConfigStrings.uni
@@ -99,3 +99,4 @@
                                         #language x-UEFI-ns "iSCSIDisplayAttemptList"
 #string STR_ISCSI_ATTEMPT_ORDER         #language en-US "New Attempt Order"
                                         #language x-UEFI-ns "iSCSIAttemptOrder"
+#string STR_ISCSI_ISID_HELP             #language en-US "The iSCSI ISID. Default value are derived from MAC address. Only last 3 bytes are configurable."
diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.c b/NetworkPkg/IScsiDxe/IScsiMisc.c
index 2c93590deb..e20fe9194a 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.c
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.c
@@ -952,7 +952,7 @@ IScsiCreateKeywords (
       CONFIGURATION_VARSTORE_ID,
       (UINT16) (ATTEMPT_ISID_VAR_OFFSET + sizeof (KEYWORD_STR) * (Index - 1)),
       StringToken,
-      StringToken,
+      STRING_TOKEN (STR_ISCSI_ISID_HELP),
       0,
       0,
       ISID_CONFIGURABLE_MIN_LEN,