Which of the following is true of external LSAs in the Junos OS?

The statement that "Type 2 external LSAs do not consider internal reachability metrics" is accurate. In OSPF (Open Shortest Path First), Type 2 External LSAs (which are also known as Type 2 External Routes) are used to represent routes to external networks, specifically those that are reachable through an ASBR (Autonomous System Boundary Router).

Type 1 External LSAs, on the other hand, do account for the internal reachability metrics because they carry information from the internal network to the external routes, focusing on the costs associated with reaching those routes from the OSPF domain. Type 2 External LSAs are characterized by being substituted for the actual metrics from the internal OSPF domain, therefore, they do not factor internal OSPF metrics in their calculations. This affects how OSPF distributes information about external networks and determines how routing decisions are made.

Understanding these characteristics is vital for network engineers as it illustrates how routing information is processed and shared among OSPF routers, specifically pertaining to how external networks are incorporated into the OSPF route decisions.