Ethereal-users: Re: [Ethereal-users] gateway primitive

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Fri, 2 Apr 2004 00:23:52 -0800
On Thu, Apr 01, 2004 at 02:48:53PM -0500, Jack Sheppard wrote:
> I am trying to use the gateway primitive as in:
> 
> gateway host cisco10
> 
> where "cisco10" is the gateway between two networks but I get the following
> error:
> 
> That string is not a valid capture filter (parse error)
> See the help...
> 
> Does anyone know what I am doing wrong?

Using the "gateway" primitive wrong.

To quote the tcpdump man page:

          gateway {host}
                 True  if  the  packet  used {host} as a gateway.  I.e., the
                 ethernet source or destination address was {host} but  nei-
                 ther the IP source nor the IP destination was {host}.  {Host}
                 must be a name and must be found both  by  the  machine's
                 host-name-to-IP-address  resolution mechanisms (host name
                 file, DNS, NIS, etc.) and by the machine's  host-name-to-
                 Ethernet-address   resolution   mechanism   (/etc/ethers,
                 etc.).  (An equivalent expression is
                           ether host {ehost} and not host {host}
                 which can be used with either names or numbers for {host} /
                 {ehost}.)   This  syntax does not work in IPv6-enabled con-
                 figuration at this moment.

with italicized values put in "{}", to make it clearer what's literal
text, i.e. the word "gateway", and what's a variable, i.e. "{host}".

So the correct syntax is

	gateway cisco10