diff --git a/roles/nhc/README.md b/roles/nhc/README.md
index 4f7ecf61a3ac22a4e867e1ad549cd16a9f355102..37b6ea18e0ea78a96142b3efb6c2c2dfaea7d9cd 100644
--- a/roles/nhc/README.md
+++ b/roles/nhc/README.md
@@ -12,7 +12,9 @@ nhc_emails: nobody@nowhere.nowhere
 nhc_email_subject: "Node Health Check" 
 
 In addition the NAT check needs two variables to be defined to be enabled  (See example)
+- ADD_NHC_NAT_CHECK has to be defined to (any) value
+- NHC_NAT_CHK_EXTERNAL_IP_ADDRESS is the address to be pinged
 
 Example:
   roles:
-  - { role: nhc, EXTERNAL_IP_ADDRESS: "118.138.246.208", ADD_NHC_NAT_CHECK: 1  }
+  - { role: nhc, NHC_NAT_CHK_EXTERNAL_IP_ADDRESS: "118.138.246.208", ADD_NHC_NAT_CHECK: 1  }
diff --git a/roles/nhc/templates/check_nat.nhc.j2 b/roles/nhc/templates/check_nat.nhc.j2
index 8f64e3aaf66584129533ff35619dc62532a9f55c..ab56e57e890ac1b64ea994f63cd372925f0e7f53 100644
--- a/roles/nhc/templates/check_nat.nhc.j2
+++ b/roles/nhc/templates/check_nat.nhc.j2
@@ -7,7 +7,7 @@ function check_nat() {
 
 
 #test NAT by pinging an external IP ADDRESS
-PING_EXTERNAL="ping -c 2 {{ EXTERNAL_IP_ADDRESS }}"
+PING_EXTERNAL="ping -c 2 {{ NHC_NAT_CHK_EXTERNAL_IP_ADDRESS }}"
  
 $PING_EXTERNAL
 RESULT=$?