ifdown on a lo (loopback) alias does not work as expected in RHEL 6.7 and 6.8

Issue

• Running ifdown on a loopback alias does not work. The command runs successfully but the alias address is not removed:

  # ip addr show lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
      inet 10.20.30.40/32 brd 10.20.30.40 scope global lo:0
      inet6 ::1/128 scope host 
         valid_lft forever preferred_lft forever
  
  # ifdown lo:0
  # echo $?
  0
  
  # ip addr show lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
      inet 10.20.30.40/32 brd 10.20.30.40 scope global lo:0
      inet6 ::1/128 scope host 
         valid_lft forever preferred_lft forever