NIC interface- IP address

koks · 05-12-2017, 09:58 AM

Hi Experts,
I made interface(eth0) down, i can see the ipv4 address(eth0) also went down (Its expected). But i unplugged the ethernet cable (as expected link went down but still the ipv4 address was reachable from that console). Its not reachable from outside. Any update why the ipv4 was reachable still??

Thanks,
Koks.

r3sistance · 05-12-2017, 10:29 AM

Need a bit more clarity here, Do you mean you can access the IPv4 address that is hosted on the server itself? If so, then of course you can still reach it from the server as that server is hosting it. If you mean something else then maybe need to clarify what you mean a bit better.

sundialsvcs · 05-12-2017, 10:42 AM

If you configured the NIC to be "at a particular IP address," then, "it's still there," even if the network cable is unplugged. You can even try to send packets through it, although the attempt will fail.

michaelk · 05-12-2017, 12:44 PM

Welcome to LinuxQuestions

To elaborate in simple terms for example if you run the ping command using the eth0 address from the console no data is actually sent over the cable so unplugging the cable has no effect.

jefro · 05-12-2017, 05:06 PM

It may be that the NIC and various tests are not exactly as separate and they appear.

Various loopback tests and some other networking never really get to nic. Software intercepts is and returns what should not work.

koks · 05-13-2017, 03:03 AM

Hi,

Thank you for the reply.
@r3sistance: I too agree, IP was reachable since the server is hosting the same.
But my question is even though the NIC went down, how it holds the configured IPv4 Address?? Since its dead it should not hold the ip address as well.

@sundialsvcs: Yes, if the ip was not reachable from outside since the NIC went down. But how come it holds the ipv4 address on NIC??

Regards,
Koks.