RHEL6 LACP bond does not function and shows link Speed and Duplex as Unknown

Issue

• Upon boot, a RHEL6 system's LACP bond is in a bad state. It has not learned the Partner MAC and each slave is shown with a different Aggregator ID. Further, in the /proc/net/bonding/<bond> output, all or some of the slaves show a Speed & Duplex of Unknown:

  $ cat proc/net/bonding/bond0 
  Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
  
  Bonding Mode: IEEE 802.3ad Dynamic link aggregation
  Transmit Hash Policy: layer2+3 (2)
  MII Status: up
  MII Polling Interval (ms): 100
  Up Delay (ms): 0
  Down Delay (ms): 0
  
  802.3ad info
  LACP rate: slow
  Min links: 0
  Aggregator selection policy (ad_select): stable
  Active Aggregator Info:
      Aggregator ID: 1
      Number of ports: 1
      Actor Key: 0
      Partner Key: 1
      Partner Mac Address: 00:00:00:00:00:00
  
  Slave Interface: eth0
  MII Status: up
  Speed: Unknown
  Duplex: Unknown
  Link Failure Count: 0
  Permanent HW addr: a2:d6:c4:04:46:01
  Aggregator ID: 1
  Slave queue ID: 0
  
  Slave Interface: eth1
  MII Status: up
  Speed: Unknown
  Duplex: Unknown
  Link Failure Count: 0
  Permanent HW addr: a2:d6:c4:04:46:02
  Aggregator ID: 2
  Slave queue ID: 0
  

• Bringing the bond interface down and back up typically corrects the issue.