We changed the names of all these a while ago, but didn't update
the onos post-install script.
JIRA: APEX-281
Change-Id: Ib617d7f3dd0879da4e89d032cd694519fc0de557
Signed-off-by: Michael Chapman <woppin@gmail.com>
   fi
 
   # get gateway mac
-  GW_MAC=$(arping ${GW_IP} -c 1 -I br-public | grep -Eo '([0-9a-fA-F]{2})(([/\s:-][0-9a-fA-F]{2}){5})')
+  GW_MAC=$(arping ${GW_IP} -c 1 -I br-external | grep -Eo '([0-9a-fA-F]{2})(([/\s:-][0-9a-fA-F]{2}){5})')
 
   if [ -z "$GW_MAC" ]; then
     echo "ERROR: Failed to find gateway mac for ${GW_IP}"