Which of the following answers can be verified as true based on the  following command output from Router R1?（）
R1#show ip ospf virtual - links
Virtual Link OSPF_VL0 to router 4.4.4.4 is up
Run as demand circuit
DoNotAge LSA alloweD.
Transit area 1, via interface FastEthernet0/1, Cost of using 3

单项选择题ABR R1 has been configured with an area 1 stub no - summary command. Which stubby area type is area 1?（）

A. Stub
B. Totally stubby
C. NSSA
D. Totally NSSA

多项选择题Which of the following is true about routers internal to a totally NSSA area?（）

A. Routers cannot redistribute external routes into the area.
B. Routers should have zero Type 3 LSAs in their LSDBs.
C. Routers should have zero Type 5 LSAs in their LSDBs.
D. Routers should learn default routes from the ABRs attached to the area.

单项选择题Router R1, an ASBR connected to the Internet and to backbone area 0, has been configured with a default - information originate command. Which of the following is true about the effects of this configuration command?（）

A. R1 will always create and flood a default route into the OSPF domain.
B. R1 will create and flood an LSA for prefix/length 0.0. 0.0/0 into the OSPF domain if R1's IP routing table has a route to 0.0.0.0/0.
C. R1 will set a flag on the LSA for the subnet between itself and one of the ISPs, noting this subnet as a default network, regardless of whether R1 has a default route.
D. R1 w ill set a flag on the LSA for the subnet between itself and one of the ISPs, noting this subnet as a default network, but only if R1 has a route to 0.0.0.0/0.

单项选择题The following output exists on Router R1, a router internal to area 1. What can you d etermine as true from the output of the show ip ospf database summary command?（）

A. The LSA was created by an ABR due to an area range command.
B. The LSA was created by an ASBR due to a summary - address command.
C. If cr eated by an area range command, the best metric for a subordinate subnet on that ABR must have been 11.
D. None of the other answers is correct.

多项选择题R1, an ABR between backbone area 0 and area 1, has intra - area routes in area 0 for 10.1.1.0 24,10.1.2.0 24, and 10.1.3.0 24. These routes have metrics of 21, 22, and 23, respectively. An engineer then adds the area 0 r ange 10.1.0.0 255.255.0.0 command under the OSPF process of R1. Which of the following is true?（）

A. R1 loses and then re - establishes neighborships with all neighbors.
B. R1 no longer advertises 10.1.1.0/24 to neighbors into area 1.
C. R1 advertises a 1 0.1.0.0/16 route into area 1 with a metric of 23 (largest metric).
D. R1 advertises a 10.1.0.0/16 route into area 1 with metric of 21 (lowest metric).