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 range 10.1.0.0 255.255.0.0 command under
the OSPF process of R1. Which of the following is true? (Choose two.)
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 10.1.0.0/16 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).
Explanation:
The area range command does not cause a failure in neighborships. Because at least one
intra-area subordinate subnet of 10.1.0.0/16 exists in R1, R1 both creates a summary route
for 10.1.0.0/16 and stops advertising LSAs for the (three) subordinate subnets. By default,
the metric of the summary is the metric of the lowest-metric component subnet.
I’d choose answer C. instead of D. based on the following:
Note about summary address metric calculation: RFC 1583 leavingcisco.com called for calculating the metric for summary routes based on the minimum metric of the component paths available.
RFC 2178 leavingcisco.com (now obsoleted by RFC 2328 leavingcisco.com) changed the specified method for calculating metrics for summary routes so the component of the summary with the maximum (or largest) cost would determine the cost of the summary.
Prior to IOS 12.0, Cisco was compliant with the then-current RFC 1583 leavingcisco.com. As of IOS 12.0, Cisco changed the behavior of OSPF to be compliant with the new standard, RFC 2328 leavingcisco.com.
http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7039-1.html
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Answer D is correct. Eigrp summary aggregate address is different from OSPF one.
You can configure a summary aggregate address for a specified interface. If any more specific routes are in the routing table, EIGRP will advertise the summary address out the interface with a metric equal to the minimum of all more specific routes.
Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfeigrp.html
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