1 files changed, 13 insertions, 8 deletions

diff --git a/examples/var_service/dhcp_if/convert2ipconf b/examples/var_service/dhcp_if/convert2ipconf
index 038b1f7f1..31e3c7fde 100755
--- a/examples/var_service/dhcp_if/convert2ipconf
+++ b/examples/var_service/dhcp_if/convert2ipconf
@@ -29,14 +29,19 @@ test "$ip" || exit 1
 # some servers do not return subnet option.
 # guess it for standard private networks.
 if ! test "$mask"; then
-        if test "$ip" != "${ip#192.168.}"; then
-                mask=16
-        elif test "$ip" != "${ip#172.16.}"; then
-                mask=12
-                # repeat for each in 172.17. - 172.31. range?
-        elif test "$ip" != "${ip#10.}"; then
-                mask=8
-        fi
+        case "$ip" in
+        10.*)
+                mask=8;;
+        192.168.*)
+                mask=16;;
+        #172.16-31.x.x
+        172.1[6789].*)
+                mask=12;;
+        172.2[0123456789].*)
+                mask=12;;
+        172.3[01].*)
+                mask=12;;
+        esac
 fi
 
 # some servers do not return router option.