Defines the ERSPAN session type. This object may not be
modified if the value of the corresponding instance of
crcERSpanSessionRowStatus is active.
'eRSpanSource' refers to a session where traffic is copied from
crcERSpanIFIndex of crcERSpanIFTable as source to crcERSpanIp
as destination.
'eRSpanDestination' refers to a session where traffic is copied
from crcERSpanIp as source to crcERSpanIFIndex of
crcERSpanIFTable as destination.