MAC address to IP Address Translation Question 1

[Guest721]

Does anyone know how to do a MAC address to IP Address Translation for a remote WAN device from a windows system (cmd line) or any free downloadable program that does this?

It's easy to do a remote MAC lookup via an IP, but I can't seem to find a way to do the MAC to IP. I tried ARp cmd but that doesn't get me anywhere. Perhaps RARP is needed?

Any help is appreciated.

 

[Comstocb]

My understanding is that is the device is remote, meaning it is a layer 3 hop away, you will not be able to determine the MAC address of that remote device. It will never be known on the network your on as it is stripped from the packet when it crosses the layer 3 boundary. The ways around this:
1. Get the remote device to report its MAC in the data of the packet returned. Don't know a convenient way to do this offhand however. Does anyone know if there is an ICMP option to get this information returned or some other way?
2. Telnet to the remote device and look it up locally
3. Telnet to a device on the same network as the remote device, such as an edge router, and look up the MAC in its table.
4. Have a tool or an agent for a tool on the remote network (such as flukes network inspector)
5. Call someone who has access to that network and ask them.
6. If the remote device is a windows machine, NBTStat -A <ip address> will return the systems MAC.

These are the ways I can think of, any other ideas?

Brian

 

[Comstocb]

I re-read your question and now I am not sure if you have the MAC and want the IP or if you have the IP and want the MAC. My above response is if you have the IP. If you have the MAC, again, you have to have some way to access the network that the device resides on except now you don't even have the luxury of being able to ping or telnet to the device. Much harder indeed in my thinking. If you do have the MAC, how did you come across it not being on the remote devices network??

Brian

 

[Guest721]

Hi Brian,

Thanks for your reply.

Sorry for any confusion, but let me try to clarify.

I'm actually trying to help someone who has a MAC address from a device on the network (actually in a different city from me but on the same company network), but needs to find out what the IP address of that device is to find out more information.

We know what subnet the device is on and the MAC address, but do not know the IP address. I had someone who has access to the routers arp the router that handles that particular subnet and was able to obtain a list of IPs and corresponding MAC addresses. I can then just find the MAC address on the list and see it's matching IP address.

I do not have access to the routers so I would like to find out if there is a way to resolve MAC addresses to IP address information myself. Through the windows cmd line, a program, or any other way. I searched the web for some programs, but didn't come up with anything I can use.

Any more info would be great.

 

[manarth]

IP addresses are routed, MAC addresses aren't. You cannot access a MAC from the other side of a router.

There is no facility to &quot;ping&quot; a MAC address - only a device on the same physical network as that MAC can give you any more information about it.


Normally, if you don't know the IP address, you use DNS to resolve to a hostname.

<marc>[ul]help us help![li]please give us feedback on what works / doesn't[/li][li]not sure where to start? click here: faq581-3339[/li][/sup][/ul][/sup]

 

[Guest721]

Thanks for your answer Marc.

 

[Comstocb]

Sound like you have someone who is on the same network as the device in question. I suggest you get a ping sweep tool and run it from your friends PC on the same network. Solarwinds and WS_PingPro are good examples but I bet there are free ones to be had on the net. If all else fails, ping the addresses one at a time by hand. Anyway, since the PC will ping all addresses in the subnet, it will have to ARP first and build a local ARP table on the PC. Then just do an ARP -A from your friends PC command line and just look for the MAC address you want.

Brian

 

[manarth]

&quot;just do an ARP -A from your friends PC command line and just look for the MAC address you want.&quot;

Whilst it is sound practice for a once off, if this is a regular lookup, Guest721 really needs a more automated system.

DNS is useful because all you need to know is a hostname to resolve an IP. Depending on the LAN situation & the purpose for the IP lookup, there may be a simpler / easier way to achieve the end result.


Guest721: If you'd like to post more about why you want to do a reverse ARP, maybe we'll have some more suggestions as to how to achieve your goal.

<marc>[ul]help us help![li]please give us feedback on what works / doesn't[/li][li]not sure where to start? click here: faq581-3339[/li][/sup][/ul][/sup]

 

[Guest721]

Brian, Marc,

Thanks for your replies again.

My friend's situation does seem to be a once off. We just wanted to find out a way to resolve a similar issue faster if it occurs in the future.

 

[tcambridge]

Have you tried checking the ARP cache on the router for the MAC address you're looking for? If that machine is actively participating in the network, it will contact the router for IP connectivity and the router will have the MAC address.

Good Luck!

Tim Cambridge
A+, CCNA, MCSA, MCSE (W2K)

 

[tryssenaar]

I have a similar problem, where I know the MAC address of the device, but nothing else. It is not active on the network either. Can anyone think of a way to find the IP address?