Hi, I am trying to understand packet filtering and I am lost in what I am reading. Quoting from page 217 of Building Internet firewalls on allowing inbound and outbound SMTP and nothing else as the example. It says as follows Rule Direction Source Dest Proto Destport Action ====================================================================== A in Ext Int tcp 25 Permit B out Int Ext tcp >1023 Permit C out Int Ext tcp 25 Permit D in Ext Int tcp >1023 Permit E Either any any any any Deny Now based on the explanations I came out with this ipchains rule but I am not sure if it it correct or not IPC=/sbin/ipchains $IPC -P Deny -l $IPC -A in -s Ext -d Int -p tcp --sport 1023: --dport 25 -j ACCEPT $IPC -A out -s Int -d Ext -p tcp --sport 25 --dport 1023: -y -j ACCEPT $IPC -A out -s Int -d Ext -p tcp --sport 1023: --dport 25 -j ACCEPT $IPC -A in -s Ext -d Int -p tcp --sport 25 --dport 1023: -y -j ACCEPT $IPC -b -s 0/0 -d 0/0 -j DENY Am I on the right track or completely away ? TIA -- Togan Muftuoglu