Question on my Cisco 2800 IP Address

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Oct 22nd, 2007
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Hi,


I had inherited a Cisco 2800 router from a previous IT Manager and unfortunately its configurations were not documented very well. I am at a point where I need to rebuild our Sonicwall firewall (sits between the router and the network) and I need the IP of our cisco router. Is there any easy way of figuring out the IP of the router, I've tried looking in the manual and guides online for the router but I'm not sure how to even connect to it. If anyone has any ideas of finding out the IP of the router that would be a big help.


Thanks,

Pete

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Richard Burts Mon, 10/22/2007 - 07:26
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Pete


There are several ways to connect to the router. If you know at least one of the IP addresses of the router then you can telnet or SSH to the router and use the command line interface on the router. You would need to have passwords (and possibly user ID - depending on how the router is configured) to access the command line interface. Or if you know at least one IP address of the router then the router may have a web interface enabled which gives you a GUI - again it depends on how the router was configured, it may be enabled or it may be disabled. Or if you do not know any IP addresses on the router there is a console interface. This is for a hard wired connection from the console port of the router to a PC. You need a console access cable, which Cisco provides, and terminal emulation software on the PC (many people use Hyperterm which comes with Windows and there are many others.


There are a couple of approaches to finding the IP of the router. I would assume that if the Sonicwall sits between the router and the network then the router is the gateway for the Sonicwall. So I would assume that you can look at the config of the Sonicwall and find its gateway address.


Another approach to finding the address would be to do a tracert from a Windows PC in the network (or a traceroute from a _nix box) to some address out in the Internet. The address of the router should show up in the traceroute output.


Or if you figure out how to access the router there is a command show ip interface brief which will show the IP addresses of all interfaces on the router.


HTH


Rick

nfpaadmin Mon, 10/22/2007 - 07:45
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Normally I would have checked the settings in the firewall but oddly enough I can no longer connect to its web interface yet its function still works.


I will try to use the console port on router. Right now there is an old US Robotics 56k modem connected to the console port through its own console port. I don't really see any use for it to be connected or why it would have been connected in the first place.


Thanks for your help and quick response!


Pete

Richard Burts Mon, 10/22/2007 - 07:54
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Pete


The reason to have a modem connected to the console port is to give you the ability to have out of band management or remote management of the router. Normally connection to the console is hard wired and requires that you are physically at the router. If you can dial the modem and connect to the console then you have a console connection while you are remotely located away from the router. And you have the ability to connect to the router and to manage (or to troubleshoot) even if there are problems with its interfaces and telnet/SSH can not access the router. In general it is a good thing.


HTH


Rick

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