The region called Ogaden is found in the eastern part of Ethiopia and is primarily inhabited by Somali ethnic groups.

Option 1, Eritrea and Sudan, is incorrect because Ogaden is not a disputed area for these two countries, their disputes have been mainly over other regions, notably the Hala`ib Triangle.

Option 2, Ethiopia and Somalia, is the correct answer. The Ogaden War (1977-1978) took place between these two countries over control of Ogaden, which Somalia wanted to incorporate into a Greater Somalia.

Option 3, Kenya and Somalia, is not correct as their disputes primarily revolved around the border areas of these two countries and not the Ogaden region.

Option 4, Ethiopia and Sudan, is also not correct as their disputes have mostly been over other regions like the Fashaga region and not Ogaden. Therefore, the correct answer is Ethiopia and Somalia, who fought wars over the Ogaden region.