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Linux determine which NIC has connectivity or not.

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Last Modified: 2013-12-16
Running Linux distro I think RH9 with VMWare ESX 3.1 server.

I have 4 NICs in this server, how can I tell which one is which?  Is there a command that will tell me the link status.  I've tried ifconfig and netstat but neither will tell me if the link is up or down.  What I was going to do is just unplug each one at a time and see which loses connectivity and then I'd know which is which.

Maybe there's an easier way.....

Thank you in advance,
Tom
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Most Valuable Expert 2015

Commented:
If you have console access you can run 'system-config-network'.

CLI 'netstat -ni' will show active interfaces.

Or you can see if traffic is passing through a NIC, 'tcpdump -i eth0'

Then check the NIC lights on the back to determine the ordering (left to right or right to left) if they are not marked.
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Commented:
Sweet, had no idea that ethtool was there.
Sometimes (depending on the module in use) ethtool won't work. For that try mii-tool

ie
eth0: negotiated 100baseTx-FD flow-control, link ok
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Top Expert 2007

Commented:
I find the output of mii-tool easier to read

mii-tool

and if you want full details

mii-tool -v

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