Re: Controlling IP forwarding

Glynn Clements (glynn@sensei.co.uk)
Sat, 30 May 1998 01:13:04 +0100 (BST)


peloy@ven.ra.rockwell.com wrote:

> What I want is to control what gets forwarded in the Linux box. This
> is: since I can't control the Cisco router, I want to set in all
> machines of the local network the default router to be the Linux box
> instead of the Cisco router, and then control there what gets
> forwarded or blocked.
>
> I am trying to acomplish this with ipfwadm but I don't really
> understand this command (very complex, IMHO).
>
> Can this be done? Can anyone send me an example on how to block,
> for example, all connections from machines in the local LAN trying to
> connect to TCP port 23 of a machine on another subnet?

ipfwadm -Fa reject -P tcp -D 0/0 23

This will prevent any traffic from being forwarded to port 23. As
connections within the LAN won't be forwarded via the Linux box, this
won't affect them.

-- 
Glynn Clements <glynn@sensei.co.uk>
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