IPchains Firewalling - Editing a Chain
This file describes the editing of chains in this module.

First, you surely want to know, what all those columns in the table are good for, so here you are:

Source
As you may guess, this column represents the source address, a packet comes from. The following port column is the source port.

Destination
The destination of a packet. For example you want http to go through but to block ftp. All those warez servers...

Protocol
This is the protocol the packet is sent in. The usual types are TCP or UDP, often also ICMP for pings, traceroute and some net watchers to check the availability of your servers. You may want to leave specific packets through, but others not. Note, that the protocol does not mean the high level protocols like http or ftp but the low level netlink protocols.

Interface
This defines the interface, the rule applies for. For input packets this is the device they came in on, the interface for forward and output packets is the device they will leave on. Perhaps there is one "trusted" interface which is allowed to deliver all packets, but another (connected perhaps to the internet) is only allowed to deliver specific packages...

S (SYN-Bit)
Indicates, whether the SYN-Bit for packets must be set, must not be set or it may be set.
If it must be set there is a X, if it must not be set there is a ! and if it may be set there is nothing.

F (Fragment)
Matches the second through the last fragment of a fragmented packet. No ports may be specified. If it must be set there is a X, if it must not be set there is a ! and if it may be set there is nothing.

L (Logging)
If set (X) packet is logged.

TOS (Type Of Service)
ipchains can change the TOS of a packet. To do this there are several possible values. This is shown in this column.