diff --git a/README.md b/README.md
index 1b5edca..97c8ff7 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,8 @@ In this case igb (ec_igb) driver is in use.
 ## add EtherCAT network interfaces
 In ETHERCATDRVR define the EtherCAT interfaces by adding `LINK_DEVICES` and `LINK_DEVICE_MACS`
 
+**NOTE**: Always specify the MACS with lower case letters!!
+
 ```shell
 DEVICE_MODULES="igb generic"
 
@@ -47,6 +49,7 @@ LINK_DEVICES="ens2f0 ens2f1 ens2f2 ens2f3"
 LINK_DEVICE_MACS="d4:f5:ef:b3:7b:d8 d4:f5:ef:b3:7b:d9 d4:f5:ef:b3:7b:da d4:f5:ef:b3:7b:db"
 ```
 
+The number of entries in LINK_DEVICES and LINK_DEVICE_MACS must be the same. If igb and LINK_DEVICE_MACS are defined then the names in LINK_DEVICES are not important but must be defined (dummy1, dummy2..). However, if generic driver is used, then the LINK_DEVICES names must correspond to the actual interface names.
 
 #  workflow for new server
 
diff --git a/WORKFLOW.md b/WORKFLOW.md
index c35d115..f88f4e1 100644
--- a/WORKFLOW.md
+++ b/WORKFLOW.md
@@ -36,6 +36,8 @@ https://git.psi.ch/controls-ci/warewulf-node-config/-/blob/master/nodes.conf
 
 **NOTE**: The simplest is to copy another host and update the needed data.
 
+**NOTE**: Always specify the MAC with lower case letters.
+
 **NOTE**: Configure only the boot network interface in nodes.conf. EtherCAT interfaces are configured in ETHERCATDRVR (see [README.md](README.md))
 
 **WARNING**: No tabs are allowed, make sure the indention is made with spaces.