Re: Finding the IP of some device on the LAN ?

"Doug Phillips" <dphill46@xxxxxxxxxxxx> wrote in
news:1171566140.102073.212460@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

On Feb 14, 10:43 am, JF Mezei <jfmezei.spam...@xxxxxxxxxxxxx> wrote:
Say I plug in some unknown gizmo (without user interface) on my lan.


If I didn't know what the gizmo was, I sure as hell wouldn't plug it
into my lan.


What would be the way to find out its IP address that it thinks it
has ?


First, find out what the gizmo is, then RTFM. I've never seen a useful
device that has no way to access its settings.

Are there reverse ARP commands where you give it the ethernet address
of a device, it sends a broadcast asking that device to identify
itself and you then know what IP it has ?

If this device is configured with an IP that is not in the same
subnet, does it implicitely mean that arp tables on that lan's host
will not include that response from the gizmo even though they may
have physically received it ?

So, how do you find out the IP address of any other device on a
network? What happens if it has the same IP as some other device --
like your router or server? If the device isn't in the same subnet,
and your routing doesn't include that net, then anything the device
says is ignored. Maybe try a sniffer if you really think it's saying
something?



This has been an interesting topic to follow, but I don't think we've
seen anything further from the OP.

Solutions seem to be:
1) Look at the DHCP/BOOTP server.
2) Look at the ARP cache of some known network device which may have seen
network traffic from this mysterious device.
3) Use a network sniffer.

If the IP address is static and outside of the local network subnet,
solution 1 and 2 are not useful.
If the real problem is that device doesn't appear to be getting an IP
address via DHCP/BOOTP, possibly because those protocols are disabled,
then it may be that the device will accept one via RARP. I've
accomplished this in the past by setting up a static ARP entry, with the
IP address I wish to use and the MAC address obtained from the case of
the device. I've used both MultiNet and Windows for the setup of static
ARP entries. I begin a continuous ping from the system with the static
ARP entry and then I power on the device (already connected to the
network.) I've had it take up to 2 minutes before getting a ping
response, but once I've gotten a reponse, I've just connected to the
device via telnet and set a new static IP address. (Actually, I think
these have always been print servers, but I'm sure there are other
devices that support this same procedure.)
.

Relevant Pages

  • Re: Reduce ARP Traffic
    ... We discovered we had a lot of Spanning Tree Protocol traffic ... lot lf ARP request traffic. ... You have a brigde to another network? ... 2)Create a simple static IP network between 1 client and the server - ...
    (microsoft.public.windows.server.networking)
  • Re: Wired and Wireless NICs on same subnet using DHCP
    ... Both nics use DHCP to get an IP ... address fom a Windows 2003 DHCP Server in that subnet. ... When you connect to the network with ONLY the wireless nic, ... Gratious ARP for the IP assigned to the wired nic!. ...
    (microsoft.public.windowsxp.network_web)
  • Re: Reduce ARP Traffic
    ... ARP, I understood it to be a part and parcel of running an IP-ethernet ... network, so I'm not too worried about that either. ... To eliminate variations between my workstations, ... Troubleshooting Client Authentication on Access Rules in ISA Server 2004 ...
    (microsoft.public.windows.server.networking)
  • Re: Reduce ARP Traffic
    ... STP is also a must for those of us running education networks where the kids ... think it's fun to knock the network down by looping the ethernet. ... server that is connected to each for redundancy. ... for ARP, I understood it to be a part and parcel of running an IP-ethernet ...
    (microsoft.public.windows.server.networking)
  • Re: Questions about 192.168
    ... any need for ARP. ... In order for your computer to talk to another computer on the LAN, ... internet, your computer sees that the requested address is not on your ... Folks on your network could be proxying ARP, ...
    (Security-Basics)