diff --git a/bin/lua/wipf/lang/en.lua b/bin/lua/wipf/lang/en.lua
new file mode 100644
index 00000000..ebcf5f0a
--- /dev/null
+++ b/bin/lua/wipf/lang/en.lua
@@ -0,0 +1,4 @@
+-- WIPF Localization: English
+
+err_conf_iprange_inc = "Bad Include IP address: line %d"
+err_conf_iprange_exc = "Bad Exclude IP address: line %d"
diff --git a/bin/lua/wipf/util/conf.lua b/bin/lua/wipf/util/conf.lua
index 2e318230..2a4c6448 100644
--- a/bin/lua/wipf/util/conf.lua
+++ b/bin/lua/wipf/util/conf.lua
@@ -1,6 +1,7 @@
 -- WIPF Configuration Utilities
 
 local wipf = require"wipflua"
+local i18n = require"wipf/util/i18n"
 local util_ip = require"wipf/util/ip"
 
 
@@ -73,9 +74,18 @@ local conf_meta = {
 
     local iprange_from_inc, iprange_to_inc =
         util_ip.ip4range_to_numbers(self.ip_include)
+    if not iprange_from_inc then
+      return nil, i18n.tr_fmt('err_conf_iprange_inc', iprange_to_inc)
+    end
 
     local iprange_from_exc, iprange_to_exc =
         util_ip.ip4range_to_numbers(self.ip_exclude)
+    if not iprange_from_exc then
+      return nil, i18n.tr_fmt('err_conf_iprange_exc', iprange_to_exc)
+    end
+
+    --local group_names, app_dospaths =
+    --    util_ip.ip4range_to_numbers(self.ip_exclude)
 
     return true
   end,
diff --git a/bin/lua/wipf/util/fs.lua b/bin/lua/wipf/util/fs.lua
index 7bd4fc90..9f73bd8c 100644
--- a/bin/lua/wipf/util/fs.lua
+++ b/bin/lua/wipf/util/fs.lua
@@ -66,9 +66,22 @@ local function path_to_dospath(path)
   return drive_to_dosname(drive) .. sub_path
 end
 
+-- Load file, run it in sandbox and return it's globals in a table
+function sandbox(path)
+  local chunk, err_msg = loadfile(path)
+  if not chunk then
+    return nil, err_msg
+  end
+  local env = setmetatable({}, nil)
+  setfenv(chunk, env)
+  chunk()
+  return env
+end
+
 
 return {
   pid_dospath		= pid_dospath,
   dospath_to_path	= dospath_to_path,
   path_to_dospath	= path_to_dospath,
+  sandbox		= sandbox,
 }
diff --git a/bin/lua/wipf/util/i18n.lua b/bin/lua/wipf/util/i18n.lua
new file mode 100644
index 00000000..72f0c5e0
--- /dev/null
+++ b/bin/lua/wipf/util/i18n.lua
@@ -0,0 +1,43 @@
+-- WIPF Internationalization Utilities
+
+local util_fs = require"wipf/util/fs"
+
+
+local current_lang, lang_strings
+
+
+local function set_current_lang(lang)
+  current_lang = lang
+  lang_strings = assert(util_fs.sandbox("lua/wipf/lang/" .. lang .. ".lua"))
+end
+
+local function get_current_lang()
+  return current_lang
+end
+
+-- Get translation text for l10n identifier
+local function tr(id)
+  return lang_strings[id] or id
+end
+
+-- Get formatted translation text for l10n identifier
+local function tr_fmt(id, ...)
+  local s = lang_strings[id]
+  if not s then
+    return id
+  end
+
+  return string.format(s, ...)
+end
+
+
+-- Set default language English
+set_current_lang("en")
+
+
+return {
+  set_current_lang	= set_current_lang,
+  get_current_lang	= get_current_lang,
+  tr			= tr,
+  tr_fmt		= tr_fmt,
+}
diff --git a/test/wipf_test.lua b/test/wipf_test.lua
index 28844e38..8c58af01 100644
--- a/test/wipf_test.lua
+++ b/test/wipf_test.lua
@@ -4,6 +4,7 @@ local sys = require"sys"
 local sock = require"sys.sock"
 
 local wipf = require"wipflua"
+local i18n = require"wipf/util/i18n"
 local util_conf = require"wipf/util/conf"
 local util_fs = require"wipf/util/fs"
 local util_ip = require"wipf/util/ip"
@@ -111,3 +112,12 @@ do
 end
 
 
+print"-- I18n"
+do
+  local id = 'err_conf_iprange_inc'
+  local text = i18n.tr_fmt(id, 3)
+  assert(text ~= id)
+  print("OK")
+end
+
+