public static int chooseIntChannelProperty(String listenAddressName, String propertySuffix, int defaultValue) {
        String globalPropertyName = "server." + propertySuffix;
        String listenAddressPropertyName = "server." + listenAddressName + "." + propertySuffix;
        Integer value = new DynamicIntProperty(listenAddressPropertyName, -999).get();
        if (value == -999) {
            value = new DynamicIntProperty(globalPropertyName, -999).get();
            if (value == -999) {
                value = defaultValue;
            }
        }
        return value;
    }
First looks for a property specific to the named listen address of the form -
"server.${addrName}.${propertySuffix}". If none found, then looks for a server-wide property of the form -
"server.${propertySuffix}".  If that is also not found, then returns the specified default value.
zuul-core/src/main/java/com/netflix/zuul/netty/server/BaseServerStartup.java