Which OSPF LSA type has a domain flooding scope?

A.
router

B.
network

C.
external

D.
summary

Explanation:
OSPF routers use Link-State Advertisement to send updates to other routers about their network connectivity. These LSAs are flooded into the network with different scopes i.e. flooded into an area, different areas etc.

OSPF uses the Type5 external link LSAs to advertise external routes originated from an ASBR. They are flooded through the whole OSPF domain (at least into the parts where they are accepted) and point packets for those external addresses to the ASBR. There is a field called Forward Address within that Type5 LSA, which is usually set to 0.0.0.0 which means that the packets should be sent directly to the ASBR.

Type 5 – External LSA – these LSAs contain information imported into OSPF from other routing processes. They are flooded to all areas (except stub areas). For “External Type 1” LSAs routing decisions are made by adding the OSPF metric to get to the ASBR and the external metric from there on, while for “External Type 2” LSAs only the external metric is used. The link-state ID of the type 5 LSA is the external network number.