Mailinglist Archive: opensuse (882 mails)

[John Andersen <jsamyth@xxxxxxxxx>]

On 12/2/2010 4:51 PM, David C. Rankin wrote:
> On 12/02/2010 06:43 PM, David C. Rankin wrote:
> > On 12/02/2010 06:15 PM, John Andersen wrote:
> > > I use my Nexus One.  Use to use my iPhone.  Lots of apps for that.
> > >
> > > When no tools at hand:
> > > ping -c 2 -b <broadcast IP>       (something like 192.168.1.255 - You need 
> > > -b option)
> > > -c 2 sends just two pings.  No need to get crazy.
> > >
> > > then immediatly do
> > >
> > > /sbin/arp -n
> <snip>
>
> I've noticed that using arpd seems to give you the best results for hosts that
> might not be up at the moment. Just start arpd with:
>
> # arpd -b /var/lib/arpwatch/arpd.db ath0
>
> Here is the differences in the results. With arp I get only 4 hosts and the
> router (.13)
>
> 18:45 alchemy:~/scr/utl/tst> ping -c2 -b 192.168.6.102
> <snip>
>
> 18:45 alchemy:~/scr/utl/tst> sudo arp -n
> Address                  HWtype  HWaddress           Flags Mask            
> Iface
> 192.168.6.121            ether   00:0F:1F:D6:03:A0   C                     
> ath0
> 192.168.6.13             ether   00:23:69:5C:FD:B4   C                     
> ath0
> 192.168.6.17             ether   00:E0:81:55:4E:1D   C                     
> ath0
> 192.168.6.147            ether   00:11:43:22:5A:25   C                     
> ath0
> 192.168.6.14             ether   00:21:85:1A:8C:FA   C                     
> ath0
>
> Using the script above, I get the whole list:
>
> 18:46 alchemy:~/scr/utl/tst> sh arpt.sh
>
> Hostname                  IP                      Mac
> archangel                 192.168.6.14            00:21:85:1a:8c:fa
> zachrys-iPhone            192.168.6.112           d4:9a:20:92:0b:f5
> gateway (Linksys)         192.168.7.13            00:06:25:5e:dd:29
> supersff                  192.168.6.121           00:0f:1f:d6:03:a0
> gw                        192.168.6.13            00:23:69:5c:fd:b4
> mail                      192.168.6.17            00:e0:81:55:4e:1d
> dcrgx2                    192.168.6.147           00:11:43:22:5a:25
> dcrgx                     192.168.6.111           00:11:43:22:4f:23
> zion                      192.168.6.19            00:0c:76:13:16:e6
> Wii                       192.168.6.115           00:1b:ea:d6:91:80
> ripper                    192.168.6.149           00:0c:76:13:90:c2

Yup.

The distro I first used this on predated arpd (or at least It wasn't installed).
Nothing is going to find a host that is unpowered, which is why arpd is cool 
because
it will record for you even if they only show up fleetingly, but of course you 
have
to have it running, which most networks probably don't.

The ping command I use serves to fill in the arp table, but in real busy 
networks
this info becomes stale and is dropped from the arp table fairly quickly.
You don't want to dawdle firing off that arp command after the ping.

The advantage is it works for non-root (unless someone hides arp) and it works 
on
windows too.


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