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Is it possible to find out if a public ip is associated with a router or a pc?

At my home i have internet connected to my pc through a netgear router. The router is connected to the internet modem. When i try to login to isp website through my router, i get authentication denied message. But if i connect my pc directly to modem the login passt hrough. I am not getting what difference the router can make?

I configured my router to use my pc mac address but still no avail.

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migrated from serverfault.com Aug 13 '09 at 8:52

This question came from our site for professional system and network administrators.

    
i cannot login to superuser.com. How do i do that? –  chappar Aug 13 '09 at 4:55
    
Contact your ISP, who will walk you through the basic configuration to get you connected. –  John Gardeniers Aug 13 '09 at 8:14
    
Superuser details can be found here blog.stackoverflow.com/2009/07/… –  Sam Aug 13 '09 at 8:43
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3 Answers

A few have suggested using nmap to detect the OS on the machine. There is an additional hint that you can use, which is the OUI number issued. Of course, there is quite a lot of overlap between makers of routers and network cards for PCs. However, it is an additional hint to help. You can get the number as the first 3 bytes of the MAC address.

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You can't get the MAC address beyong the first router. –  Kristof Provost Aug 13 '09 at 10:37
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nmap

nmap will let you "crawl" an IP... so that could help shed some light on things for you.

It sounds to me though like you might have a firewall or port forwarding issue of some kind perhaps?

Perhaps the router is blocking you. When you take the router out of the loop everything works as expected, right?

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yes. The problem is only through router –  chappar Aug 13 '09 at 4:26
    
Depending on your router type you may want to try CLONING the MAC ID of your cable modem to the router. –  KPWINC Aug 13 '09 at 5:04
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nmap has a -O option that attempts to find the OS of the scanned device.

Don't run nmap against hardware where you don't have permission to run it, however.

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