Which of the following answers is true based on the information in the output from B1?

Router B1, an internal router in area 1, displays the following output. The only two
ABRs connected to area 1 are performing Type 3 LSA filterinG. Which of the following
answers is true based on the information in the output from B1?
R1# show ip route 10.1.0.0 255.255.0.0 longer-prefixes
! Legend lines omitted for brevity
10.0.0.0/8 is variably subnetted, 17 subnets, 3 masks
O 10.1.2.0/24 [110/658] via 10.10.13.1, 00:00:32, Serial0/0/0.1
O IA 10.1.1.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2
O IA 10.1.3.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2

Router B1, an internal router in area 1, displays the following output. The only two
ABRs connected to area 1 are performing Type 3 LSA filterinG. Which of the following
answers is true based on the information in the output from B1?
R1# show ip route 10.1.0.0 255.255.0.0 longer-prefixes
! Legend lines omitted for brevity
10.0.0.0/8 is variably subnetted, 17 subnets, 3 masks
O 10.1.2.0/24 [110/658] via 10.10.13.1, 00:00:32, Serial0/0/0.1
O IA 10.1.1.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2
O IA 10.1.3.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2

A.
A Type 3 LSA for 10.2.2.0/24 was filtered by both ABRs.

B.
A Type 3 LSA for 10.1.2.0/24 was not filtered by both ABRs.

C.
A Type 3 LSA for 10.1.3.0/24 was not filtered by at least one ABR.

D.
A Type 3 LSA for 10.1.1.0/24 filtered by both ABRs.

Explanation:
The output lists all R1’s routes for subnets within the range of
10.1.0.0–10.1.255.255, whose prefix lengths are longer than /16. One answer lists subnet
10.2.2.0/24, which is not in this range, so the output cannot be used to confirm
nor deny whether the subnet was filtereD. R1’s route for 10.1.2.0/24 is an intra-area
route by virtue of not listing an IA code by the route; Type 3 LSA filtering only filters
Type 3 LSAs, which routers use to calculate interarea routes, so the output tells
us nothing about any filtering of 10.1.2.0/24. The output shows a single interarea
route for 10.1.3.0/24, so at least one ABR has flooded a Type 3 LSA for this route.
Additionally, the output confirms that at least one ABR flooded a type 3 LSA for
10.1.3.0/24, or the output would not show an IA route for 10.1.3.0/24. So, the type 3
LSA for 10.1.3.0/24 was not filtered by both ABRs.



Leave a Reply 0

Your email address will not be published. Required fields are marked *