ignore spp_portscan

[LaraCroft <laracroft () zaralinux com>]

Hello 

I'm trying to ignore a ip, i have put this lines in the snort config:  (my line to star snort is snort -D -o -c /etc/snort.conf)   

pass icmp 199.183.24.194/32 any -> any any 
pass tcp 199.183.24.194/32 any -> any any 
pass udp 199.183.24.194/32 any -> any any 
and 
var DNS_SERVERS [199.183.24.194/32] 
preprocessor portscan-ignorehosts: $DNS_SERVERS 

but the snort is still puting in my alert log the ip:  


[**] spp_portscan: PORTSCAN DETECTED from 199.183.24.194 (STEALTH) [**]  07/23-09:43:03.172213 
[**] spp_portscan: portscan status from 199.183.24.194: 1 connections 
across 1 hosts: TCP(1), UDP(0) STEALTH [**] 
07/23-09:43:07.726826 
[**] spp_portscan: End of portscan from 199.183.24.194: TOTAL time(0s)  hosts(1) TCP(1) UDP(0) STEALTH [**] 
07/23-09:43:11.866921  

what must i do to ignore this ip? 

thx  [:)]  

Alexandra