Which of the following is an OSPF configuration parameter that is used on an ABR, but not on an
internal router?

A.
A virtual link to area 0.

B.
OSPF summarization command.

C.
default-cost extension to the area command.

D.
no-summary extension to the area stub command.

E.
None of the other alternatives apply

Explanation:
The no-summary extension of the area stub command is used only for ABRs connected to totally
stubby areas. It prevents and ABR from sending summary link advertisements into the stub area.
This option is used for creating a totally stubby area.
Topic 3, Implement an eBGP based solution, given a network design and a set of
requirements