The network topology is as follows.
In normal state, MOC-NE40E-2 have a static default route to the firewall, and advertise OSPF default route (not always default route) to other 3 NE40E. And when firewall run OSPF to the routers, and then delete the OSPF on the firewall and MOC-NE40E-2, other 3 routers cannot receive OSPF default route from MOC-NE40E-2, until add OSPF default-route.-advertise again. And all other 3 routers OSPF default route's FA address still on the firewall address which is unreachable.
In current implementation of HUAWEI, the following conditions are checked about the generating of default as-external-lsa when “network” or “undo network” is configured.
(1) Whether current ospf process is active or not.
(2) Whether area type is correct to establish an as-external-lsa.
(3) Whether the “default-route-advertise” command is configured.
(4) Whether there is an active default route in routing table.
(5) Whether the policy is passed.
(6) Choose a suitable forwarding address.
(6.1) Whether the default route’s outgoing interface is physical active.
(6.2) Whether the outgoing interface is enabled in the same ospf process.
(6.3) Whether the outgoing interface is on broadcast network or on p2p network.
(6.4) Whether the outgoing interface is on the same network as the nexthop.
So when the outgoing interface is inactive in protocol, default as-external-lsa should be deleted.
(1) In normal state, all OSPF peer states are FULL, even when enable OSPF between firewall and NE40E.
(2) The problem is only happening when undo network this IP segment. (3) MOC-NE40E-2 still generates default as-external-lsa with forwarding address on firewall(the static default route net-hop).
(4) The static default route on MOC-NE40E-1 is deactivated because ?(5) The default ospf route on MOC-NE40E-1 is deleted because of forwarding address is unreachable. So the flow is dropped.
In following software version, OSPF protocol can add another check item as follows.
(6.5) Whether the outgoing interface is active in protocol.