Used in conjunction with ping thanks Krizz , this is a good basic walk through. I can't go wrong with these steps! I'm sorry but Currently my preferred method if the device isn't listed in Spiceworks: There was a time when I was a baby admin and I didn't want to raise alarms by installing a scanner that I wrote a batch file yes, that long ago that PINGed every IP on a subnet, then immediately ran ARP redirecting output to a text file.
But that depends on the device in question being set to respond to PING requests. This does not work for any host on the other side of a router. Any hosts on the other side of the router will show the routers MAC address. I realize this is an old topic, but someone like myself may be looking for an answer. I became admin of a network with little over devices, which none of the cabling was mapped. I was told I was responsible for the cabling, so I began looking for a way other than toning out all the cables.
I was fortunate to have Cisco switches and Windows Server Furthermore I could also get the computer name from DHCP and correlate that to which user was on the machine using PDQ inventory to see who was logged in to the machine. Most of this of course depends on the devices being in use. I am interested in this thread, hopefully someone can help. There are 4 types of arp message: So, that being said, is it possible to manually send a rarp request? Sort of a arp based ping? There is arping, but we need rarping Of course, I understand that I can't arp outside my default gateway, but if there is a rarp request, how is it used inside the local network?
Thanks to whatever guru can explain what we're missing. My instance where I found this useful was after updating the firmware on a switch remotely via TFTP, the IP of the switch would change making pinging redundant, obviously. Trying a network scan over Spiceworks or rescanning the single device would not update the IP and I needed an alternate way to find it. This method worked perfectly. Thank you.
Hopefully this helps those trying to understand the purpose of this practice and how it was in-fact useful. I understand the issues in attempting to use a MAC address to locate a device from outside of its local network. The hardware configuration is: The router is connected to Comcast with a Motorola SB modem. Comcast assigns a system wide dynamic IP. There is no static IP. On initial setup, a WiFi connection is first established between the thermostat and the router. It is then possible to read or set thermostat values using Total Connect Web pages.
Does anyone understand how this works with Total Connect? This post was extremely helpful, thanks itdownsouth: I used show interface to find MAC addresses on our switches reason for this is poor network documentation and mis-labeled switchports and wall jacks Tedious, but found 5 or 6 now seeing hexadecimal thoughts now though By the way, the reason this is working great for me is the lack of routers -- all switches, so if you have only one subnet like we do, this will do -- otherwise, you will probably need to login to the router or switch on the other side of the router to find MAC address tables on the other networks.
You may not be able to see them all on the local host, as far as arp -a on the local host, but looking up the arp or hosts tables on switches and routers could be a possible solution for those with multiple subnets.
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Use SuperScan to do a bulk ping of the entire network range. SuperScan 3 I recommend is a free tool by McAfee. It should be able to find most devices on the network. You can specify the range to scan and scan across subnets.
How to Find a MAC Address Using an IP Address
I won't try to share all the features because quite frankly I don't know them all. I can tell you exactly how I designed it. It's actually quite simple. Nothing is sent back to the unit. The unit is allowed access to the Internet via your setup and the router. As long as the unit has permission to make an outbound connection it will work. What happens is the unit makes a report to the server. If it needs to make a request then it gives the server a unique key.
The server puts any needed data in an xml readable and the thermostat or quite a few other devices hits that URL a few seconds later the device told the server where it would pick up that info.
Get mac address of a remote computer
You can use the arp command to view and modify the ARP table entries on the local computer. This may display all the known connections on your local aream network segment if they have been active and in the cache. The arp command is useful for viewing the ARP cache and resolving address resolution problems. Displays current ARP cache tables for all interfaces.
How to Use an IP Address to Find a MAC Address
The -N parameter is case-sensitive. Identical to -a. To delete an entry in a table for a specific interface, use the IfaceAddr parameter where IfaceAddr is the IP address assigned to the interface. There are two types of ARP entries- static and dynamic. Most of the time, the computer will use dynamic ARP entries. This means that the ARP entry the Ethernet MAC to IP address link has been learned usually from the default gateway and is kept on a device for some period of time, as long as it is being used.
Software in your computer will predefine these static entries such as multicast addresses and broadcast addresses. Because of management headaches and the lack of significant negatives to using dynamic ARP entries, dynamic ARP entries are used most of the time. When starting up, some operating systems like Windows perform a gratuitous ARP to detect any duplication with its own IP address. These problems are difficult to isolate and track down.
Use the arp -a command to display the mappings in the ARP cache. If you know the Ethernet address for the remote computer you wish to use, you can easily determine whether the two match.
If not, use the arp -d command to delete the entry, then use Ping with the same address forcing an ARP , and check the Ethernet address in the cache again by using arp -a. If both computers are on the same network, you will eventually get a response from the imposter computer. If not, you might have to capture the traffic from the impostor host with Network Monitor to determine the owner or location of the system. Troubleshooting the ARP cache can be difficult because the problems associated with it are so often intermittent.
Purpose of the ARP Ping tool
The exception to this is when you find that the wrong host responds to a command, perhaps when you use a Netuse or Telnet command. The symptoms of invalid entries in the ARP cache are harder to reproduce and involve intermittent problems that only affect a few hosts. The underlying problem is that two computers are using the same IP address on the network.
You only see the problems intermittently because the most recent ARP table entry is always the one from the host that responded more quickly to any particular ARP request.
To address the problem, display the ARP table using the arp -a command. Since addresses assigned by DHCP do not cause address conflicts like those described here, the main source of these conflicts is likely to be static IP addresses. Maintaining a list of static addresses and corresponding MAC addresses as they are assigned can help you track down any address conflict just by examining the IP and MAC address pairs from the ARP table and comparing them to the recorded values.
It is primarily used in Frame Relay and ATM networks, in which Layer 2 addresses of virtual circuits are sometimes obtained from Layer 2 signaling, and the corresponding Layer 3 addresses must be available before those virtual circuits can be used. RARP is used to obtain the Layer 3 address of the requesting station itself for address configuration purposes.