diff -ur iproute2.orig/ip/ifcfg iproute2/ip/ifcfg
--- iproute2.orig/ip/ifcfg	2000-04-16 19:42:50.000000000 +0200
+++ iproute2/ip/ifcfg	2002-07-07 18:45:42.000000000 +0200
@@ -21,7 +21,7 @@
 ABCMaskLen () {
   local class;
 
-  class=${1%%.*}
+  typeset -i class=${1%%.*}
   if [ "$1" = "" -o $class -eq 0 -o $class -ge 224 ]; then return 0
   elif [ $class -ge 224 ]; then return 0
   elif [ $class -ge 192 ]; then return 24