Multi-Exit Discriminator Selector. This parameter
indicates whether or not a MULTI_EXIT_DISC will be
accepted for a network matching this filter and, if
accepted, what value to use. 'pass' indicates that the
value will be advertised as received. 'override' indicates
that the value in wfIpBgp4AnnounceMultiExitDisc will be used.
'generate' indicates that the value in
wfIpBgp4AnnounceMultiExitDisc will be used if a MED attr.
is not present in the BGP-4 update message.
'delete' indicates that the metric will be removed
if present in the attribute list. Only valid if
'action' is 'accept'.