200-301 · Question #1373
Refer to the exhibit. Router R1 receives static routing updates from routers A, B, C, and D. The network engineer wants R1 to advertise static routes in OSPF area 1. Which summary address must be adve
The correct answer is D. 10.1.40.0/23. To effectively summarize static routes from various sources (A, B, C, D) into OSPF area 1, the summary address 10.1.40.0/23 is the most appropriate.
Question
Refer to the exhibit. Router R1 receives static routing updates from routers A, B, C, and D. The network engineer wants R1 to advertise static routes in OSPF area 1. Which summary address must be advertised in OSPF?
Exhibits
Options
- A10.1.41.0/25
- B10.1.40.0/24
- C10.1.40.0/25
- D10.1.40.0/23
How the community answered
(51 responses)- A2% (1)
- B14% (7)
- C8% (4)
- D76% (39)
Why each option
To effectively summarize static routes from various sources (A, B, C, D) into OSPF area 1, the summary address 10.1.40.0/23 is the most appropriate.
10.1.41.0/25 is too specific, covering only 128 addresses within the 10.1.41.0 range, and would not summarize routes from 10.1.40.0/24.
10.1.40.0/24 covers 256 addresses from 10.1.40.0 to 10.1.40.255, which is insufficient if routes from the 10.1.41.x range also need to be summarized.
10.1.40.0/25 is too specific, covering only 128 addresses within the 10.1.40.0 range, and would not encompass a broader set of static routes.
A 10.1.40.0/23 summary address covers the IP range from 10.1.40.0 to 10.1.41.255, which is the smallest contiguous block that can encompass multiple /24 or /25 subnets that would logically be advertised from routers A, B, C, and D within the 10.1.4x.x range.
Concept tested: OSPF route summarization calculation
Source: https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13689-14.html
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