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Howto discover Cisco 2501 IP

Posted on 2004-10-04
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Last Modified: 2008-02-20
I have a preconfigured (by someone else) Cisco2501 router.
no idea what's the IP & any of the configurations.
it's connected to my LAN but it's not in my subnet.
at the moment I can't connect it's RG-45 to any COM because of it's phisical location.
is there any way that I can find the IP of the router (I can connect RG-45 to console directly from a laptop if it would help)
thx
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Question by:chuku
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39 Comments
 
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Expert Comment

by:JFrederick29
ID: 12216383
You'll need the console cable and the enable password of the router to view the configuration and determine the IP address.

Do you have the enable password?  If so, or if none is set, you can console into the router using your laptop and hyperterminal.

Once connected to the router:

router>enable
Password:
router#show run

The running configuration will display the IP address assigned to each interface.
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by:chuku
ID: 12216436
I know all about the last part but once again, the problem is getting to the router.
the console can only be connected to RG-45 connection which for hyperterminal, require an IP for connection.
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Expert Comment

by:JFrederick29
ID: 12216479
When you connect via the console port on the router using the rollover cable it does not use IP.  You can hyperterminal to the router without knowing any IP information.

You need the console/rollover cable and the RJ-45/DB9 connector to connect your laptop to the router.

Once you are physically connected to the console port on the router.  Create a hyperterminal session using the appropriate Com port and settings:

Bits per second = 9600
Data Bits = 8
Parity = none
Stop Bits = 1
Flow Control = hardware
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by:chuku
ID: 12216720
JFrederick29, once again I point my problem:
there is no way for me to connect the router to a COM port on my laptop.
I can only connect RG-45 from the console to RG-45 on my laptop!
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by:JFrederick29
ID: 12216919
Don't you have another laptop or PC with a serial port you can use just for this initial configuration?  You need to be able to console into it.
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Expert Comment

by:GreatWhiteOne
ID: 12217200
What type of switch do you have on your network.  If you know the ip address of the switch the router is conected to and the switch is a cisco switch, you can type show cdp neighbor and it will show you the router.  Than you can type" show cdp neighbor int fa0/1 details" and it will give you the ip address of the router(of course replace fa0/1 with the interface the router is on).

Do you know the MAC address of the interface on the router?

Hope that helps.
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by:chuku
ID: 12217389
GreatWhiteOne,
the router conencted to the network via Catalyst switch.
using 'show cdp neighbor' show 'no entry found'
is the MAC address show phisicaly on the router's box?
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Expert Comment

by:NicBrey
ID: 12218640
Most people these days turn cdp off for securioty reasons. Probably the case here then. Even if you could get the IP address off the router, you would still not be able to do anything casue you dont have the vty or enable passwords.

The only way to get all that is as JFrederick29 said, via a rolled console cable.
Then read this link to recover the passwords:
http://www.cisco.com/en/US/products/hw/routers/ps233/products_password_recovery09186a0080094795.shtml
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by:GreatWhiteOne
ID: 12219378
I agree with the above.  If you do not have the telnet or enable password, then there is no real point to trying to get the IP address on it.  The MAC address is usually on a sticker the back of the router or on the side, and you can use ARP to get the IP address.

Thanks,
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Expert Comment

by:PennGwyn
ID: 12219780
The "RG-45" (I believe you mean RJ-45) "console" port on the router is NOT an Ethernet port.  It is a *serial* port, and is usually used with a "rolled" cable and a 9-pin or 25-pin converter into a COM port.  (If your laptop doesn't have a COM port, you may want to get a USB-to-COM adapter for it, less than $10.)  There is no connection between the console port and your laptop's Ethernet port that can work!

If the router has a network port (i.e. not "console" or "aux") plugged into your network, then from an adjacent Cisco device you may be able to type "show cdp neighbors" and learn the IP address of the router.  That's unless CDP is turned off, either in this router or your other equipment.

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by:chuku
ID: 12220602
one of my serial ports have a COM connector, that's the port connected to my network using RJ-45 (PennGwyn)
how does the MAC structure should look like? it's got all kind of stickers on the back
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by:chuku
ID: 12288205
I understand that it's impossible, no one could give any solution for that problem.
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Expert Comment

by:JFrederick29
ID: 12289155
chuku, bottom line is that you need to get a computer with a serial port so you can console into the router.  It is invaluable when working with routers and switches.  I don't believe there is an alternative solution to the question and therefore I believe it was answered.  That's my opinion anyway.
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Expert Comment

by:NicBrey
ID: 12289566
Agree with JFrederick29.  I believe we are correct in our answers. Apart from connecting to the console port with a rolled console cable, there is NO way to get any info of the router if you don't have an IP address. And even with an IP address, you need SNMP to be configured with a read/write communtity string on the router.
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Author Comment

by:chuku
ID: 12290727
JFrederick29 & NicBrey,
I understand that you both realy want these points but if you'll read again the original request you'll understand that I know that connecting the console would do the job but I can't do so & must find a way getting there by IP.
non of the answers above gave such solution which, in my opinion, should get these points.
since the admin asked for an expert opinion, we'll wait for him to say the last words :)

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Expert Comment

by:NicBrey
ID: 12290815
I understand your point. Trust me, there is no way of doing that. If it was that easy to get router configs people would be hacking backbone routers on the internet by the minute :)
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Author Comment

by:chuku
ID: 12295652
I can phisycally connect RJ-45 to a PC
I can't get the connection work since I don't know the IP

the Phisycal connection can be created via a bridge, not directly & that's why I said that I can't connect a COM port, besides, my laptop doesn't contain a COM port...

the connector on the serial AUI port of the router allow me to use RJ-45 cable to the network, if I have set the IP correctly (which I didn't)

hope it's clearer now :)
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Expert Comment

by:AutoSponge
ID: 12328868
[quote]my laptop doesn't contain a COM port...[/quote]

Find that very hard to believe.  How do you connect an mouse, modem, or anything else external--just USB?  If so, get another computer--you can't support routers without a COM port.

The RJ-45 CONSOLE port on the router should be connected to your DB-9 COM port on the PC via rollover cable.  If you don't have a rollover ending in DB-9, get the DB-9 to Rj-45 adapter and use an Rj-45 to Rj-45 rollover cable.
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Expert Comment

by:AlbertaBeef
ID: 12328966
The com port on your laptop should have pins like this:  If you have one like this, it's a COM port...

o o o o o
 o o o o
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Expert Comment

by:AlbertaBeef
ID: 12328980
remember, com port/serial port are the same thing in this case.  it's an interchangeable term.  I have yet to see a laptop without a com/serial port, but I suppose it's possible.   What make/model of laptop do you have?

There's a special cable that comes with the router thats designed to connect the 9 pin serial/com port (as shown in my post above) to the RJ45 on the back of the router.  That's the interface you need.  You can't use a straight RJ45 cable to your laptop, it's not going to interface properly.
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Author Comment

by:chuku
ID: 12329183
1st I want to remind you that my laptop can't get to the router because of the phisycal location of the router but...
my laptop have these oprts: PS2 (for mouse), paralel (for printer), VGA connector & USB.
that's it!
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Expert Comment

by:AutoSponge
ID: 12329896
Ok, if you can't go to the site you have the following options (I'm pretty sure this is all of them):

1.  Order a vendor dispatch for "Hands & Eyes" with a laptop.  Make sure the tech is Cisco trained.  If you don't have a contract for your remote sites with a technical vendor, you may be able to setup a call out but it will cost more.

2.  Get a plane ticket.  Visit the site yourself.  Take the laptop.

3.  Have someone at the site aquire (you ship or they buy) the appropriate cable for a laptop or PC and connect to the console port of the router.  You can walk them through it--it's really not hard.

4.  Have someone at the site order/buy a modem (like a USR V.Everything) and configure it to receive calls and pass through to COM at 9600 8,N,1.  You'll still need the rollover cable to go from the serial port on the USR to the router (may need DB-25 though instead of DB-9).  Plug the modem into a local POTS line and try dialing into console.  Your connection to the modem should also be 9600.  If you get garbage, chances are the console port speed is 115200 and dial connection won't work.

5.  Have the other site unhook the router and put it in a box.  They go to a UPS Store and ship it to you.  Once you have it, log into console and do all the normal pw break stuff to aquire whatever info you need.  Reconfigure it and send it back to the site where they just (hopefully) plug and play.
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Author Comment

by:chuku
ID: 12330305
talking about cinical...
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by:AutoSponge
ID: 12330431
Ok, if you don't like that I thought of something else...

If the box is actively moving data (just not on your subnet) and SOMEONE can arp it, have local work stations check their tables (arp -a on windows) and look for a cisco MAC header in there.

Cisco Headers:
00000C
00067C
000671
00070D
001007 - Catalyst
00100B
00100D - Catalyst 2924
001011 - 75xx series
00101F - Catalyst 2901
001029 - Catalyst 5000
00102F - Cisco 5000
001079 - 5500 router
00107B
0010A6
0010F6
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Author Comment

by:chuku
ID: 12331465
you still miss the point - since I don't know the IP, I don't know to which subnet it belongs.
it's not accessable from the LAN which tell me that it's on a different subnet,
but I can't guess each & every subnet out there, can I?
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Expert Comment

by:AutoSponge
ID: 12331927
You could use a network discovery tool, but it could take a while and generate a lot of bogus results because your're going to have to tell it all networks.  That's when you need a really high end tool that had the ability to match vendor MACs and label devices as workstation or router, etc.  Only problem there is, it's not a surefire way to find the IP.  If, for instance, the router is on a separate VLAN than the discovery tool, you won't be able to reach it.  If you want to try this anyway, just google 'ip discovery tool' and you should get some ideas of where to download one.  Just remember, it has a low chance of working, so don't invest a lot of money unless you think you can gain other benefits from it.
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Expert Comment

by:AutoSponge
ID: 12335650
I tried really hard on this one.  The fact is, that no one wants a way for you to get a box's IP or config information from outside the network unless you have physical access--it constitutes an enormous breach of security on several levels.  If anything other than what we presented here was possible I'm sure all would be UNpleasantly surprised.
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Author Comment

by:chuku
ID: 12336464
AlbertaBeef, ee_ai_construct & all!
reading again my original Q would explain once & for all what is my problem:
RJ-45 can be attached but that's not the solution & got nothing to do with the solution!!!
the problem is that I have no idea what is the IP, it's not in my subnet (which could be easy to find) and here is the main point which you all avoid: I can't connect the CONSOLE port (stated in this clear to me but not enough to you: "at the moment I can't connect it's RG-45 to any COM because of it's phisical location")
discovering the IP on such cases can only be done with console connection. once this connection is unavailable, there is a problem which no one here talked about & no solution (even a wrong one) was suggested.
so, maybe the Q wasn't clear enough but you didn't get to the point at no stage of this long Q&A
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Author Comment

by:chuku
ID: 12338336
jFrederick29 wrote about connecting the console & getting the IP while I have no phisycal access to the console port.
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Accepted Solution

by:
JFrederick29 earned 250 total points
ID: 12338352
chuku, if you don't have physical access/console abilities and you don't know the IP address, you can't get into the router.  That's the answer to your question.  It may not be the answer you are looking for but nonetheless, it is the answer.
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Author Comment

by:chuku
ID: 12338421
at last someone understand my problem!
either I wasn't clear enough or there is no solution. it mighgt be both.
anyway, I didn't get a solution & unless you think that "there is no solution" is a valid answer, no one earned it here.
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