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i have a domain controller with 2 NIC's. For some reason when i ping it from other computers, both on and off the domain it is responding from an ipaddress that doesnt belong to either of them.

Does anyone know why?

WAN IP: xxx.xxx.xxx.xxx LAN IP: 80.0.0.2 Responding IP: 80.9.9.1.

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3 Answers

Is it possible a NIC has a second address assigned? Check with ipconfig /all.

Alternately, is the machine responding via a NAT'd gateway? Try using a traceroute, and see if anything else is inserted into the path. tracert <target>

If neither are those are helpful, check the MAC address of that odd IP. arp -a will show you all MAC/IP pairs, and arp -a <IP> will do just one. Does that MAC address match one of the target NICs? If not, does it match any other machines? Perhaps something else is responding in its stead? Perhaps because you've accidentally assigned this server's IP to another machine?


--Chris

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Without knowing more about your machine I'd guess it's either RRAS, as NinjaBomb mentioned, or perhaps a management/monitoring address that some servers piggy back on top of the "normal" IP address assigned to a NIC.

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Maybe Routing and Remote Services or Terminal Services running? I think this would create another visible IP address to create VPN connections.

EDIT

Almost exact same question here: http://serverfault.com/questions/95210/why-was-my-ping-answered-by-a-different-ip-address-than-the-one-pinged

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RRAS is a good possibility but not TS, which doesn't create any additional addresses. –  John Gardeniers Jul 9 '10 at 13:30
    
John Gardeniers - You are right. My bad. –  NinjaBomb Jul 9 '10 at 16:38
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