Mailinglist Archive: opensuse (882 mails)

[John Andersen <jsamyth@xxxxxxxxx>]

On 12/3/2010 9:24 AM, Greg Freemyer wrote:
> On Fri, Dec 3, 2010 at 10:04 AM, İsmail Dönmez <ismail@xxxxxxxxxxx> wrote:
> > On Fri, Dec 3, 2010 at 4:19 PM, James Wright <jamfwright@xxxxxxxxx> wrote:
> > > I generally do something like this:
> > >
> > > for host in 10.1.0.{1..254}; do fping $host; done
> >
> > How about ping -b 255.255.255.255 ?
> >
> > Regards,
> > ismail
>
> I don't think you can trust pings of the broadcast IP.
>
> ================================
> On my network:
> Both
> ping -b 255.255.255.255
> and
> ping -b 10.0.1.255
>
>  only show 5 hosts:
>
> ===
> WARNING: pinging broadcast address
> PING 10.0.1.255 (10.0.1.255) 56(84) bytes of data.
> 64 bytes from 10.0.1.249: icmp_seq=1 ttl=64 time=0.289 ms
> 64 bytes from 10.0.1.248: icmp_seq=1 ttl=255 time=0.311 ms (DUP!)
> 64 bytes from 10.0.1.183: icmp_seq=1 ttl=64 time=1.21 ms (DUP!)
> 64 bytes from 10.0.1.2: icmp_seq=1 ttl=64 time=1.22 ms (DUP!)
> 64 bytes from 10.0.1.3: icmp_seq=1 ttl=64 time=2.20 ms (DUP!)
> ===
>
> But:
> fping -g 10.0.1.0/24 -a -s -c 1 -r 1
>
> Reports 24 IPs in use:
> ===
>      256 targets
>       24 alive
>      232 unreachable
> ===
>
> which seems a lot more realistic in my office.
>
> fyi: the broadcast ping is missing both openSUSE and windows machines
> at a minimum.  Seems to get routers and printers.
>
> Greg
>
>
> broadcast is only showing 5 machines.


Because of the dups, you can't rely on the output of pinging the
broadcast.  That is why you have to follow it with an "arp -n"

Furthermore, you don't want to sent out a stream of pings to
broadcast, two is plenty to populate your arp table.

Pinging each host separately, per James's example requires evaluating
a rather messy return, and David was looking for something that
he could put in a script.




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