Tips for finding IP Address of Cisco 2800 series Router

[Zydain]

I have a Cisco 2800 series router that no one knows the IP address of or the username and password to.  It's not the gateway on the PC as it's pointed to a Cisco ASA, which I have full access to.  I assume there's a setting in the ASA that points to the IP of the 2800 router?

[balaji.bandi]

One option takes the MAC address from the connected port and Look for IP address ? even if you know IP address if you do not know the credential what is the Point.

go for password recovery using console cable :

https://www.cisco.com/c/en/us/support/docs/routers/2600-series-multiservice-platforms/22188-pswdrec-2600.html

[Richard Burts]

We certainly do not have much detail to work with on this issue. The suggestion from @balaji.bandi addresses the issue of not knowing the user ID or password used for the router. But the original post seems to be asking more for suggestions about what IP address the 2800 is using. It is unfortunate that we do not know what kind of interfaces and how many interfaces the 2800 has. There seems to be a suggestion that the 2800 has an Ethernet interface and that the interface might be on a network where there is also an ASA. If that is the case then I would suggest this series of steps:

1) on the ASA enable debug for arp

2) power cycle the 2800

3) when the 2800 boots up it should send a gratuitous arp out its Ethernet interface

4) the debug output on the ASA will hopefully see that arp from the router and reveal its IP address.

[Zydain]

Well, ultimately I'm just trying to review the current config in preparation for implementing a new Cisco 4321 Router.

[Zydain]

Thanks for the reply.  I've tried to connect to the Console port on the router with the settings I believe are recommended:

Your PC terminal emulation program is configured for 9600 baud, 8 data bits, 1 stop bit, no parity,
and flow control is set to “none.”

Unfortunately, I keep just getting a Terminal Window that's blank.  I'm using Putty along with a Light Blue console cable connected to a laptop through a USB adapter.  I've downloaded the driver for the adapter and am using COM3, which I found in Device Manager.  Any idea if I'm missing something here?

[Richard Burts]

There are sometimes issues in trying to use the console connection with a usb. If you connect to other Cisco devices with that console cable does it work there?

[Leo Laohoo]

2800 router stores it's config in the CF. 

What happens if the CF gets ejected and gets "read" by using a multi-card reader?

[Giuseppe Larosa]

Hello @Zydain ,

if the C2800 router is connected to a Cisco switch you can use

show cdp neighbor

You need to identify the port the router is connected to.

To find out what port(s) it is connected to you can power off it and check what ports are gone down on the switch(es)

Then you powr on again the router and wait few minutes.

and show cdp neighbor detail can tell you the IP address the device has on the LAN inteface connected to the switch.

to find the IP address on the C2800

For recovering credentials follow the password recovery procedure suggested by @balaji.bandi .

Check also @Leo Laohoo  suggestion, however if the router has service password encryption enabled you will see an hash of the password and not the password.

Hope to help

Giuseppe

[Chris_R1]

If the Layer 3 path is simply PC --> ASA --> Router --> Internet.  What is the second hop in a traceroute to 8.8.8.8?

[Leo Laohoo]

How easy is it go get physical access to this router?

[Zydain]

Well, I think I may have been on a wild goose chase.  I just started at this company and it turns out this router is 100% managed by a third party.  I'm assuming it's entirely locked down lol.  I'll find out more later in the week.

[Richard Burts · Accepted solution]

Thanks for the update. If the router is 100% managed by a third party then there would not be anything you could do with it.

[Richard Burts]

Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.