Why 'ifconfig' output shows an "UP" flag for an interface which is not in use and has no link on it ?

Solution In Progress - Updated -

Issue

  • Devices are showing UP flag even though there isn't a link on that interface, ethtool as well does not show any link.
eth1      Link encap:Ethernet  HWaddr B8:2A:72:xx:xx:xx
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state UNKNOWN qlen 1000
    link/ether b8:2a:72:xx:xx:xx brd ff:ff:ff:ff:ff:ff

# ethtool eth1
Settings for eth1:
[...]
Link detected: no

Environment

  • Red Hat Enterprise Linux (Any Version)
  • NetworkManager in use

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