How to find which are the NICs have physical link UP ?

Scenario -1: Assume you have 4 network Card in you Linux box. 2 out of 4 network card are connected with switch but you do not know which of them ?

Scenario -2: Network team says that they have connected a cable in one of 4 NICs of Linux box. how to find in which NIC?

• Bring up all interfaces

   for i in $(ifconfig -a|grep ^eth|cut -d " " -f1) ; do ifup $i ;done

• Take note of MAC addresses of all NIC
  

  grep "" /sys/class/net/eth*/address 

• Check Link status. Use any of below.(use any one of below)
  

  grep "" /sys/class/net/eth*/carrier 2>/dev/null  #Status 1 is means linked
  grep "" /sys/class/net/eth*/operstate 2>/dev/null
  for i in $(ifconfig -a|grep ^eth|cut -d " " -f1) ; do 

      echo $i;ethtool $i| grep Link;done| paste - -
  mii-tool 2>/dev/null
  ip link show |grep LOWER_UP