Bond not keeping MTU of 9000 after ifdown/ifup - See also BONDING_MASTER_UP_ENSLAVE option

On SLES 11 SP3 with a bonded interface configured to have the MTU set to 9000,
doing an ifdown/ifup on that bonded interface will result in the MTU setting being reset back
to the default of 1500, unless the BONDING_MASTER_UP_ENSLAVE option is set to yes.

The ifcfg-bonding man page does not mention this symptom/issue/requirement.

ifcfg-bonding at the time of this writing said this:

BONDING_MASTER_UP_ENSLAVE
         This option allows to revert the change and set the master "link
         up" before enslave.  Older kernels required  bonding  master  in
         "link up" state while enslave.  Recent kernels have been adopted
         to allow enslave in down state and this seems  to  work  better,
         faster  and  avoids  several  (false) problems, because in "link
         down" state, several async actions aren't started at "set up" or
         enslave  time  of  the  first  slave  and  need to be aborted or
         repeated later.

In the configuration file for the bond (E.g. /etc/sysconfig/network/ifcfg-bond0)
set the BONDING_MASTER_UP_ENSLAVE='yes'

Example Configuration:

Network cards:

ifcfg-eth0
BOOTPROTO='none'
BROADCAST=''
ETHTOOL_OPTIONS=''
IPADDR=''
MTU=''
NETMASK=''
NETWORK=''
REMOTE_IPADDR=''
STARTMODE='auto'
USERCONTROL='no'

ifcfg-eth1
BOOTPROTO='none'
BROADCAST=''
ETHTOOL_OPTIONS=''
IPADDR=''
MTU=''
NETMASK=''
NETWORK=''
REMOTE_IPADDR=''
STARTMODE='auto'
USERCONTROL='no'

ifcfg-bond0
BONDING_MASTER='yes'
BONDING_MODULE_OPTS='mode=802.3ad miimon=100'
xmit_hash_policy='layer3+4'
BONDING_SLAVE0='eth0'
BONDING_SLAVE1='eth1'
BOOTPROTO='none'
BROADCAST=''
ETHTOOL_OPTIONS=''
IPADDR=''
MTU='9000'
NAME=''
NETWORK=''
REMOTE_IPADDR=''
STARTMODE='auto'
USERCONTROL='no'
PREFIXLEN='16'
BONDING_MASTER_UP_ENSLAVE='yes'

Restart the network or ifdown/ifup the bonded interface to have the new setting take effect.