ifconfig(8): note about supported format for IPv4 addresses (RHBZ#176661)

man/en_US/ifconfig.8

@@ -39,6 +39,11 @@ supported address families include
 (Novell IPX) and
 .B netrom
 (AMPR Packet radio).
+All numbers supplied as parts in IPv4 dotted decimal notation may be decimal,
+octal, or hexadecimal, as specified in the ISO C standard (that is, a leading 0x
+or 0X implies hexadecimal; otherwise, a leading '0' implies octal; otherwise,
+the number is interpreted as decimal). Use of hexadecimal and octal numbers
+is not RFC-compliant and therefore its use is discouraged.
 .SH OPTIONS
 .TP
 .B -a