Re: tcpdump - performs what on initialization?

[Jefferson Ogata <Jefferson.Ogata () noaa gov>]

Guy Harris wrote:
> On Thu, Apr 10, 2003 at 06:36:51PM -0700, Derek D. Newton wrote:
>
> > I currently administrate some Cobalt RaQ 4 servers, which occaisionally
> > stop responding via their network interface. This has been a mystery so
> > far, but may have something to do with ARP'ing. ifconfig down /up brings
> > the RaQ back up, but so does simply running tcpdump.
>
>
> Do any *other* ifconfig operations that might do something to the
> hardware also bring it back up (turning promiscuous mode on or off with
> ioctl, turning allmulti mode on or off, changing the media type)?
>
> I don't know offhand whether ifconfig down/up does, although I wouldn't
> be surprised if they do; turning promiscuous mode on, as tcpdump does by
> default, definitely does things to the hardware.

For one thing ifconfig down/up sends a gratuitous arp. If gratuitous arp 
solves the problem, you may have an IP address conflict on your LAN.

--
Jefferson Ogata <Jefferson.Ogata () noaa gov>
NOAA Computer Incident Response Team (N-CIRT) <ncirt () noaa gov>

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