help with tcpdump cmd syntax

[Karol Kwiatkowski]

On 08/04/2006 14:56, fbsd_user wrote:
> I tried 
>    tcpdump -i rl0 src host 218.166.163.180 -w /usr/tcpdump.data
>    tcpdump -i rl0 host 218.166.163.180 -w /usr/tcpdump.data
>    tcpdump -i rl0 src ip 218.166.163.180 -w /usr/tcpdump.data  
> 
> but got syntax error msg with no hint of what was wrong
> 
> If I remove the -w stuff it works. Meaning it prints to the screen.
> But I want to write to file
> 
> Can you help me out here on the syntax error?

Have a look at 'tcpdump -h' (or man, of course). Expression (i.e. 'src
host 218.166.163.180') is the last argument. This should work:

tcpdump -i rl0 -w /usr/tcpdump.data src host 218.166.163.180


> One other thing. When does tcpdump get access to the packet?
> 
> My firewall has a block log rule for that ip address. 
> Does tcpdump see the packet before ipfilter ipnat does?

Yes. I'm not familiar with kernel code, but I can perfectly see all
packets with tcpdump.

HTH,

Karol

-- 
Karol Kwiatkowski  <freebsd at orchid dot homeunix dot org>
OpenPGP: http://www.orchid.homeunix.org/carlos/gpg/0x06E09309.asc

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