capturing packets on 250mb link

[Vlad GALU]

On 4/28/08, Ganbold <ganbold at micom.mng.net> wrote:
> Vlad,
>
>
>  Vlad GALU wrote:
>
> > On 4/28/08, Ganbold <ganbold at micom.mng.net> wrote:
> >
> >
> > > Hi all,
> > >
> > >  What is the best way to capture packets on 250mb link?
> > >  What kernel features/modules or tools (less CPU/RAM overhead) should I
> use?
> > >
> > >
> >
> >    Given your OS version, I'd say that setting the BPF buffer size to
> > around 1MB and setting the monitor flag on the capture interface would
> > give you very good results. In that combination we've been doing
> > packtet capture at gigabit speeds without packet loss.
> >
> >
>
>  Thanks Vlad. So then it means something like following will work in our
> case:
>
>  #sysctl net.bpf.bufsize: 1048576
>  #ifconfig bge1 monitor up
>  #tcpdump -i bge1 -s0 -w capture.log -C 2048 -W 100
>
>  Correct me if I'm wrong here.


    Yes, it should do the job. However I can't understand why you want
a snaplen of 0, as 68 should be the minimum to accomodate the
ethernet+ip+tcp/udp headers.

>
>  thanks,
>
>  Ganbold
>
>
>
> >
> >
> > >  I have FreeBSD 7.0-STABLE machine (
> > >  CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2822.51-MHz 686-class CPU),
> > >  FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
> > >  1GM RAM, ad2: 76319MB <Maxtor 6L080M0 BANC1G10> at ata1-master
> SATA150).
> > >
> > >  #uname -an
> > >  FreeBSD ng1.micom.mng.net 7.0-STABLE FreeBSD 7.0-STABLE #3: Sat Apr 26
> > > 14:08:06 ULAT 2008     tsgan at ng1.micom.mng.net:/usr/obj/usr/src/sys/NG
> i386
> > >
> > >  #pciconf -lv|more
> > >  ...
> > >  bge0 at pci0:2:0:0:        class=0x020000 card=0x1659103c chip=0x165914e4
> > > rev=0x11 hdr=0x00
> > >   vendor     = 'Broadcom Corporation'
> > >   device     = 'BCM5721 NetXtreme Gigabit Ethernet PCI Express'
> > >   class      = network
> > >   subclass   = ethernet
> > >  ...
> > >
> > >  Are there any considerations on hardware?
> > >
> > >  thanks in advance,
> > >
> > >  Ganbold
> > >
> > >  --
> > >  Cats, no less liquid than their shadows, offer no angles to the wind.
> > >
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> > >
> > >
> >
> >
> >
> >
>
>
>  --
>  Look out! Behind you!
>


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