Find an IP address having only the MAC address

Hi again,

I've been searching google for a while about this issue, but I'm still 
too confused.

My goal is to discover the IP address of the LAN interface of a Cisco 
1721 router (it's located at the office where I work).

I know the MAC address because it's written in a sticker at the bottom of 
the router. But I don't know the password to the router admin console :(

The router's LAN interface is connected to a Sun workstation that has two 
NICs (one of them connected to the cisco and the other connected to a 24-
port switch). The Sun machine works as a firewall (its password is also 
unknown)

The possible solution I've thought is to turn off the router, connect a 
PC with a sniffer directly to the LAN interface of the Cisco and turn it 
on again.

I'm assuming that the Cisco sends an ARP packet at bootup to check if 
anyone is already using the IP it wants. I know that Windows does that, 
but, what about Cisco? Do they do the same? 

And, is this the proper method to discover the IP address, or are there 
better methods?

Thanks a million.
Kind regards.
0
Leolo
10/7/2004 12:27:27 AM
grc.techtalk.packetsniffing 559 articles. 0 followers. Follow

9 Replies
428 Views

Similar Articles

[PageSpeed] 28

"Leolo" <another@example.com> wrote in message
news:Xns957B19070B57losthighwaycom@204.1.226.254...

> I'm assuming that the Cisco sends an ARP packet at bootup to check if
> anyone is already using the IP it wants. I know that Windows does that,
> but, what about Cisco? Do they do the same?
>
> And, is this the proper method to discover the IP address, or are there
> better methods?

Did you try the Cisco site?  They have a ton of information.

-- 
Robert
GRC Newsgroups/Guidelines/No Regrets
http://news.grc.com/news.exe?cmd=article&group=grc.techtalk&item=116183
0
Robert
10/7/2004 1:57:38 PM
On Thu, 7 Oct 2004 00:27:27 +0000 (UTC), Leolo <another@example.com>
wrote:

>Hi again,
>
>I've been searching google for a while about this issue, but I'm still 
>too confused.
>
>My goal is to discover the IP address of the LAN interface of a Cisco 
>1721 router (it's located at the office where I work).
>
>I know the MAC address because it's written in a sticker at the bottom of 
>the router. But I don't know the password to the router admin console :(
>
>The router's LAN interface is connected to a Sun workstation that has two 
>NICs (one of them connected to the cisco and the other connected to a 24-
>port switch). The Sun machine works as a firewall (its password is also 
>unknown)
>
>The possible solution I've thought is to turn off the router, connect a 
>PC with a sniffer directly to the LAN interface of the Cisco and turn it 
>on again.
[snip]

If you have a sniffer, why not put a hub between the Sun and the Cisco
and watch all the packets that go between them.  Unless I am missing
something, You should be able to see the IP address for both the Sun
and the Cisco interfaces.
0
John
10/7/2004 2:32:09 PM
If you run 'ipconfig' for windows or 'ifconfig' for unix/linux then
it will show the 'Default Gateway' among other information. Would the
IP address of the 'Default Gateway' correspond to the LAN interface of
the router?????
                  -- John Paul
0
John
10/7/2004 5:37:35 PM
"Robert  Wycoff" wrote:

>> And, is this the proper method to discover the IP address, or are there
>> better methods?
> 
> Did you try the Cisco site?  They have a ton of information.

I didn't search the Cisco site because I don't have the password to access 
the configuration of the router.

However, I think I'll take a look at it just in case they have some sort of 
trick for "remembering" "forgotten" passwords... :)

Regards.
0
Leolo
10/7/2004 7:58:55 PM
John Guynn wrote: 

> If you have a sniffer, why not put a hub between the Sun and the Cisco
> and watch all the packets that go between them.  Unless I am missing
> something, You should be able to see the IP address for both the Sun
> and the Cisco interfaces.

Thanks for the suggestion. I'll ask my friends, maybe someone has a hub (I 
only have switches)

Cheers.
0
Leolo
10/7/2004 8:00:29 PM
"John Paul Giordano" wrote:

> If you run 'ipconfig' for windows or 'ifconfig' for unix/linux then
> it will show the 'Default Gateway' among other information. Would the
> IP address of the 'Default Gateway' correspond to the LAN interface of
> the router?????

The problem is that all the PCs in the LAN are using the Sun firewall as 
their "Default Gateway" (none of them are connected directly to the Cisco 
router). I already know the IP address of one of the NICs of the firewall 
(it's 172.21.96.3) but I'd like to know the IP address of the other NIC.

Kind regards.
0
Leolo
10/7/2004 8:02:51 PM
In Xns957BDFA23D6ADlosthighwaycom@204.1.226.254
Leolo mused:
> "Robert  Wycoff" wrote:
>
>>> And, is this the proper method to discover the IP address, or are
>>> there better methods?
>>
>> Did you try the Cisco site?  They have a ton of information.
>
> I didn't search the Cisco site because I don't have the password to
> access the configuration of the router.
>
> However, I think I'll take a look at it just in case they have some
> sort of trick for "remembering" "forgotten" passwords... :)

<http://www.cisco.com/en/US/products/hw/routers/ps221/products_installat
ion_guide_chapter09186a008007e57a.html>

The magic words for searching for such things on the Cisco website are
'password recovery'.
0
PnG
10/7/2004 8:50:24 PM
On Thu, 7 Oct 2004 20:00:29 +0000 (UTC), Leolo <another@example.com>
wrote:

>John Guynn wrote: 
>
>> If you have a sniffer, why not put a hub between the Sun and the Cisco
>> and watch all the packets that go between them.  Unless I am missing
>> something, You should be able to see the IP address for both the Sun
>> and the Cisco interfaces.
>
>Thanks for the suggestion. I'll ask my friends, maybe someone has a hub (I 
>only have switches)
>
>Cheers.

If your switch has support for port monitoring or promiscious (sp?)
mode you won't need a hub to sniff that segment.  Just put the switch
in between the Sun and Cisco, set the port monitor to monitor the port
that the Cisco is plugged into and start capturing packets.  Sooner or
later (probably real quickly) you'll know the IP address of both the
Sun and the Cisco.

John
0
John
10/8/2004 2:38:02 PM
Leolo wrote:
> My goal is to discover the IP address of the LAN interface of a Cisco
> 1721 router (it's located at the office where I work).
> 
> I know the MAC address because it's written in a sticker at the bottom of
> the router. But I don't know the password to the router admin console :(

This would suggest that you aren't the administrator of the router, nor the
firewall. I would suggest leaving them alone.

Something non-invasive you could try would be a traceroute out through the
firewall. This should reveal at least one of the IP's of each device.

Note, also, that on the firewall<->cisco link there are two IP addresses.
There is the external interface on the firewall and the internal interface
on the router. One or both of these IP addresses might be of interested.

You could also check for SNMP on the firewall.

Regards,
Sam
0
Sam
10/10/2004 7:29:56 AM
Reply:

Similar Artilces:

how to find ip address from mac address?
It happened more than once. At a customer's office, there is a device with an unknown ip address. We know its mac address. The ip address might be different from the network. For example, the customer's network might be 10.1.0.0/16, whereas that device might have the ip address 192.168.200.123/24. For example, it might be a managed switch that has kept its default ip address. So, it works as a switch, but I cannot manage it. Apart from a sniffer, is there a (free?) software that can scan the network and find ip addresses of all hosts, and/or only of those whose mac address ...

IP Address allocation by mac address
Is it possible to give a specific mac address a fixed IP address when it requests an address from the DHCP server? mike.dawson@scarborough.gov.uk schrieb: >Is it possible to give a specific mac address a fixed IP address when it >requests an address from the DHCP server? Yes. Just create an ip-address-object with manual assignment type in the DNS/DHCP management console. Enter the mac-address, unload and reload the dhcpsrvr module and release and renew the address at the workstation. Important: Don�t touch the client identifier field, when creating the object. J...

finding the mac address or physical address
I am writing a web page for internal use. I am trying to find out the physical address of the people that hit my webpage inside our intranet. I know I can get the mac address using external IP address but that isn't what I need. We have IP address such as 10.1.5.107 and I need to know the physical address. Also I can't outsource the code to a webserves or something like that for security purposes. Does anyone have any clues. Thanks i m not so sure about this also..but i come to an url http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=391&lngWId=10 hope that...

Virtual IP Address (Mac Addressing)
We are planning a 26node cluster Groupwise implementation early next year. After meeting with our Network people, one of them posed the question if Server A (connected to Switch A) fails over to Server B which is connected to Switch B (Will the virtual mac IP address that fails over to Server B be recorded correctly). I was under the impression that the application layer managed it, but we need clarification for Netware. Thanks. Novell's fail-over works by only moving the IP address of a resource and not the MAC address. Therefore, the fail-over is completely transparent ...

Ip addresses linked to MAC addresses?
Hi, I recently decided to install a router onto my internet connection, (partially because of my Shields Up results, and partially because my linux computer acting as a router was a bottleneck (ISA ethernet cards.. eww)) Anyway, I plugged it in, booted it up, and noticed that my IP address had changed. Now, nowhere in my internet access does it say anything about static IP address, but my IP address hadn't changed for quite some time. (Somewhere in the range of 1-2 years) I thought that this was too much of a coincidence, so I took a closer look at my LinkSys router, and saw a WAN ...

Get IP address and MAC address
Hi there! How can get ip address and mac address from command shell without root attributes(I can't use 'ifconfig'). Thank you in advance. -- [Adri�n C�rdoba] ------------------------------------------------------------------------ aecordoba wrote: > Hi there! > How can get ip address and mac address from command shell without root > attributes(I can't use 'ifconfig'). > Thank you in advance. > > /sbin/ifconfig -- Vahis aecordoba wrote: > Hi there! > How can get ip address and mac address from command shell wi...

IP address vs MAC address
Ok somebody explain this to me. I understand how IP addresses are issued(well sort of...lol) Is it one IP address to one MAC address?(not accounting for non routable IP space) I understand there can only be one WAN facing IP address per machine/MAC/NIC/etc realizing multiple NICs possible on one computer. If that is the case then how can say a Comcast DHCP server keep from issuing an IP to a MAC address that another provider has already issued an IP for? In this case perhaps someone has made up a MAC address to use in their router for cloning purposes. Or does it really ...

ip address, mac address, agent name
Hi It seems that I was able to print a report showing IP Address, MAC address and Agent Name all on the same page...Did I make that up? Does anyone know how to do that? Thanks, Kat On Mar 15, 5:16 pm, mepr...@speakeasy.net wrote: > Hi > It seems that I was able to print a report showing IP Address, MAC address > and Agent Name all on the same page...Did I make that up? Does anyone know > how to do that? Well, the MAC address would really be tough as NDPS/iPrint has no need for the MAC address and as such does not record that information anywhere. If the pritner i...

How to get MAC address & IP address?
Dear all how to get the MAC address & IP address using PowerBuilder 6.5? thanks! Michael On Wed, 16 Jan 2002 22:42:51 +0800, "Michael" <michaell@hknet.com> wrote: >Dear all > > how to get the MAC address & IP address using PowerBuilder 6.5? > thanks! > >Michael > For IP address see http://eric.aling.tripod.com/PB/tips/pbtip14.htm -- Boris Gasin [TeamSybase] mailto:bgasin@dynamictechgroup.com Close to NJ? Join the NJ Sybase Tools User Group http://www.njpbug.org/njpbug/join/join.asp On Wed, ...

Finding MAC and IP address.
In my ASP.Net 2003 application. When client clicks on a button call Show IP Address. Then my software should show him his PC's MAC and IP Address both. How to do this? Try to look into the links to get IP address and MAC address for your reference. http://forums.macosxhints.com/showthread.php?t=782 http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/cnet/cnbd_trb_nqgq.mspx?mfr=true You should encapsulate the ARP command to get MAC & IP address in asp.net by programming....

Windows software to convert MAC address to IP address?
Hi all. For the life of me, I can't remember what the name of the software that will take a MAC address and give you back the IP address if the equipment with the MAC address is on the local network. A friend suggested setting a static ARP listing for a MAC address on my computer with an unused IP address, but that didn't work. Help? - Phil "Philip H. Schlesinger" <pschlesi@REMOVE-uci_ME.edu> wrote in message news:dvut6p$2jsu$1@news.grc.com... > Hi all. For the life of me, I can't remember what the name of the > software > that...

Asisgn IP address based on wildcard MAC addresses
We are using NetWare 6.5 DHCP in our environment. I would like to assign IP addresses to PCs based on the particular manufacturer ID in the MAC address, can this be done? I tried but the DNS/DHCP management console wouldn't accept the wildcard character in the MAC addresses field. Is there any way to workaround it? Will import accepts wildcard MAC? Thanks. AFAIK, th DHCP protocol does not support what you want, in any implementation, as it is not part of the DHCP standards. bd NSC Volunteer SysOp Thanks Brad. No problem. bd NSC Volunteer SysOp Hi,...

DHCP assigning the same IP Address to Mutiple Mac Addresses
Is it possible in DHCP to assign the same IP Address to multiple Mac Addresses, ie. a laptop docked using the docking station NIC and a laptop undocked using the built-in NIC I have an application that checks security based on the IP-address that is assigned to the user. thanks, Chris Chris, AFAIK this isn�t possible. You have to add two different manual assignments to the nics. Joerg Joerg is correct, although you may be able to use a MAC Address override so that the machine has the same MAC address regardless of how it is connected. Check your OS d...

Web control for catching IP address and MAC address
Hi guys. I would like to know if any of you know a link or maybe have a library which allows me to use a textbox for enter an IP Address or a MAC address??. I've been searching on the web but all of the examples are for windows applications or they are masks for the normal textbox but they don't include the Control type for an IP address or a MAC address. Please help with this.  You would need to make a composite control of 4 textboxes.Don't forget to click "Mark as Answer" on the post that helped you.This credits that member, earns you a point and marks you...

Web resources about - Find an IP address having only the MAC address - grc.techtalk.packetsniffing

File:Ipv6 address.svg - Wikipedia, the free encyclopedia
I, the copyright holder of this work, release this work into the public domain . This applies worldwide. This file contains additional information, ...

Barack Obama outlines counter-terrorism plans in rare Oval Office address; vows to 'destroy' Islamic ...
US president Barack Obama brands Islamic State fighters thugs and killers in a rare address to the nation in the wake of last week's California ...

The backwards notion that Obama was late for the glamorous 2015 Kennedy Center Honors because he needed ...
Here's the standard presentation of that notion in People Magazine , replete with video, from which I grabbed this still. But I think the address ...

Figure out how to address your cover letter - Business Insider Deutschland
... a specific individual. Just because a job posting omits the name of the person in charge of the hiring process doesn't mean you should address ...

Obama speaks on ISIS, gun control, tolerance in Oval Office address - Videos - CBS News
... shows terrorism is now in a new phase. He promised to destroy anyone who tries to harm Americans. It was the president’s first address from ...

Clinton to address terror protection
As domestic terror fears rise, Hillary Clinton is set to explain how she will protect Americans, reports NBC News.

President Obama's Address: 'Freedom Is More Powerful Than Fear'
Here is the full text of his speech, as provided by the White House. Tonight, I addressed the nation from the Oval Office on my top priority ...

In weekly address, Obama asks Americans to 'stay true to who we are' in fight against terrorism
x YouTube Video This week, like last week, President Obama devoted his weekly address to the fight against terrorism. As I said in my speech ...

Obama’s Sunday Address Watched By 46 Million Viewers
... Obama 's Sunday night primetime speech might have, according to GOP White House candidates, been too little too late – and why give the address ...

Philips and Cisco form global strategic alliance to address EUR1 billion office lighting market
... of Things (IoT) in modern offices. This alliance brings together Philips' LED based connected lighting system with Cisco's IT network to address ...

Resources last updated: 12/17/2015 4:44:50 AM