The Rule and kernel routing scheme view
This figure represents a view of the linux routing.
A packet arrives at your computer always through the pre routing block: here linux decides the future of the new arrived:
- it can be destined to our machine and reach the input block;
- it can be forwarded to another machine and reach the forward block;
A packet is locally generated by your linux computer, for example by your web browser:
- it will pass through the output block;
Both the locally generated packets and the forwarded ones will pass through the post routing block.
Next to each block, one can see some statistics about the packets processed in that ambit.
Actions available on the rule and linux routing view widget.
- Move your mouse over the blocks to obtain information and help on the right panel (in the figure you can see the two blue-gray widgets Information and help);
- Left Click on a block to visualize the statistics pertaining to that block. Actually, if you click on a the input, output or forward block, a plot is displayed in place of the help widget, and it represents the blocked packets through that block. See the Note below to know how to switch back to the help view after you activated the statistics widget.
- Right Click on a block to be able to add a new rule pertaining to that stage. If you are not the administrator it is normal that you aren't allowed any action on the pre and post-routing stages. On the other hand, the root user can normally add Network address translation rules on the pre and post routing hooks.