Need to find IP Address of NAS device

Answered Question
Mar 15th, 2012

Hi Guys,

I have a NAS device which has a static IP Address but it was not documented and now we cannot connect to it. Can someone please tell me how to find the IP Address of this device? I know the port on the Switch it's connected to?

Any help will be greatly appreciated.

Thanks,

Lake

I have this problem too.
0 votes
Correct Answer by hobbe about 2 years 1 month ago

Hi

You do not need the ip address of the unit.

If you do what I told you before with setting up the arp table your computer will talk to the address thinking it is the correct address. say your NAS thinks it is the 192.168.0.100/24(the /24 means that the subnetmask is 24 bits ie 255.255.255.0) with mac address a0-a0-a0-a0-a0-a0

Your computer is 192.168.168.0.50/24 with mac address a1-a1-a1-a1-a1-a1

You do not know that the NAS is 192.168.0.100 but you know the machine has the mac address a0-a0-a0-a0-a0-a0.

Now you can setup a static connection between your computer 192.168.0.50 and the NAS by utilising the arp command in windows. since you do not know the address you take whatever address is not used fx 192.168.0.200.

arp -s 192.168.0.200 a0-a0-a0-a0-a0-a0

now you connect to the NAS by using 192.168.0.200

in the config of the NAS you will most likely find out the address that it is realy having.

Good luck

HTH

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hobbe Thu, 03/15/2012 - 15:09

Hi

There are several ways to talk to the device.

1) You can set a static ip address to the mac address of the device and speak to that "ip"

on windows it is the command

arp -s ipadress_of_your_choise the_unit_macaddress

(since you know the port you can findout the mac address on that port with Show mac-address-table | i portid where port id = the port it is setup in.)

2) You can reload the NAS device, (or pull the network cable on it) when it comes up it will most likely send out a gratitious arp and that will tell you what it think it has for ipadress

3) You can ping every address in the network and check your arp cache for the mac address, that will tell you what ip it responds to.

Good luck

HTH

darren.g Thu, 03/15/2012 - 17:35

Lakeram Harrypersaud wrote:

Hi Guys,

I have a NAS device which has a static IP Address but it was not documented and now we cannot connect to it. Can someone please tell me how to find the IP Address of this device? I know the port on the Switch it's connected to?

Any help will be greatly appreciated.

Thanks,

Lake

Is it a layer 2 or layer 3 switch?

You could do something like

switch# show mac address-table | include

Put in the interface number of the interface the NAS is connected to - for example, on my 3750X if I wanted to find the device connected to port g1/0/30, I would do

switch# show mac address-table | include 1/0/30

This'll give you the MAC address of the device connected to the port concerned

Then, if it's a layer 3 switch, do this

switch# show ip arp | include

and that'll give you the IP address.

If you don;t have a layer 3 switch, you'll need to do the MAC to IP check on your layer 3 device/router - which means the syntax might be different - but once you've got the MAC address, finding the associated IP address from your network kit is trivial.

If the device is not currently in the ARP table, then you can PING the broadcast from the switch (again, I'm doing this from my 3750X) by doing

switch# ping 192.168.1.255

assuming you have a /24 subnet. Of course, put your own subnet in the address. This will give you a response for every device directly connected to the switch, and then you can do the MAC to IP lookup again.

Cheers.

lharrypersaud_2 Fri, 03/16/2012 - 09:00

I now have the mac address of the device but i still cannot find the ip address? The switch is Catalyst 2960 layer 2 switch.

any help will be greatly appreciated.

Thanks,

Lake

INEMINEMINEMINEM Fri, 03/16/2012 - 09:17

Hello,

The easy way to find the IP address of the NAS is connect the device to the Network (Switch), and then use a port scan to find IP address of the devices that are live in the network.

Turn off all unnecessary equipments, to decrease the devices found in the port scan. If you do this, you will have a clear idea of the IP´s in your network.

Good Luck.

Regards

Correct Answer
hobbe Sun, 03/18/2012 - 01:26

Hi

You do not need the ip address of the unit.

If you do what I told you before with setting up the arp table your computer will talk to the address thinking it is the correct address. say your NAS thinks it is the 192.168.0.100/24(the /24 means that the subnetmask is 24 bits ie 255.255.255.0) with mac address a0-a0-a0-a0-a0-a0

Your computer is 192.168.168.0.50/24 with mac address a1-a1-a1-a1-a1-a1

You do not know that the NAS is 192.168.0.100 but you know the machine has the mac address a0-a0-a0-a0-a0-a0.

Now you can setup a static connection between your computer 192.168.0.50 and the NAS by utilising the arp command in windows. since you do not know the address you take whatever address is not used fx 192.168.0.200.

arp -s 192.168.0.200 a0-a0-a0-a0-a0-a0

now you connect to the NAS by using 192.168.0.200

in the config of the NAS you will most likely find out the address that it is realy having.

Good luck

HTH

darren.g Sun, 03/18/2012 - 19:55

Lakeram Harrypersaud wrote:

I now have the mac address of the device but i still cannot find the ip address? The switch is Catalyst 2960 layer 2 switch.

any help will be greatly appreciated.

Thanks,

Lake

You need to look on the routing device (I.E. the router for the subnet) in its ARP table.

Cheers.

INEMINEMINEMINEM Sun, 03/18/2012 - 06:26

Hello,

Since all the folks like very much arp layer 2 of the OSI model look my response for your problem, and find your IP address!

I hope this time you completely resolve your problem, ok

Regards,

Carlos Rodrigues

viningele Sun, 03/18/2012 - 06:36

There are serverl iPad apps like IP Scanner, Ping and more that will ping the subnet or any specific range you want.  It returns the addresses, description (name) on the device and its MAC address.  Very useful for see everything active on a network.

lharrypersaud_2 Tue, 03/20/2012 - 07:56

I used Hobbe's theory and that worked. I truely apppreciate all of you guys help. It was a great learning experience.

Thanks,

Lake

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Posted March 15, 2012 at 12:35 PM
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