   ,     Internet,  -
      -s () 
:

# iptables -t NAT -A POSTROUTING - ethO -s 192.168.0.0-192.168.0.32

-j MASQUERADE

    -s 192.168.0.0-192.168.0.32 ,  
    IP-   .

    
  Internet

 DNAT (NAT )   ,  -
  Internet     LAN.    
 SMTP-   192.168.1.33  HTTP- (Web-)   
192.168.1.34.     TCP; SMTP   25, 
HTTP   80,     TCP-    25
 80.    ,       -
,   DNS        
LAN.       PREROUTING  NAT (-A
PREROUTING -t NAT):

# iptables -A PREROOTING -t NAT -p tcp dport 25

to-source 192.168.0.33:25 -j DNAT

# iptables -A PREROUTING -t NAT -p tcp dport 80 to 192.168.0.34:80 -j DNAT

   ,     TCP
(-p tcp)     25 ( , --dport 25)  80 ( -
, dport 80).

 to-source   ,    PREROUTING  OUTPUT
 NAT.         , 
.     MASQUERADE  SNAT,     -
  ,   ,   .

 ,      , ,    
    DDoS- (. )    Internet,  
          .



 iptables    ,  -
     .  iptables   -
   ,    ;     -
.         ,  .
     ,     
  .

    : Filter, NAT  Mangle.  Filter (-
  )         -
.  NAT (Network Address Translation table    )

 25. iptables:                                         775