The value of tmnxOspfIfCfgMTU specifies the desired size of the
largest packet which can be sent/received on this OSPF interface,
specified in octets. This size DOES include the underlying IP
header length, but not the underlying layer headers/trailers.
Setting tmnxOspfIfCfgMTU to a value of zero (0), causes the agent
to recalculate the default MTU size which can vary based on the
current setting of tmnxPortMode and tmnxPortEncapType variables
for the port to which this OSPF interface is bound.