This key attribute specifies which protocol the export policy applies
to. If it is set to all, that means this export policy will apply all
routes in the IP routing table.
Example:
vr/1 ip ospf export/1 with
advertise Status = block
protocol = bgpExternal
bgpAsId = 3
peerAs = 5
This policy specifies that all routes learned from EBGP Peers that
are originated from AS 3 should not be advertised to AS 5.