Refer to the exhibit.
A company would prefer all Internet-bound OSPF routed traffic to use ISP ABC with ISP DEF as a
backup. As the network consultant, what three configuration changes should you make? (Choose
three.)
A.
The default-information originate command should be configured on router B1 and B4.
B.
The default-information originate command should be configured on router B2 and B3.
C.
If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to
1.
D.
If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to
25.
E.
The metric type value should be set to type 1.
F.
The metric type value should be set to type 2.
Explanation:
Routers B2 & B3 need to advertise a default route to the Internet for “inside” OSPF routers so we
should use the “default-information originate” command with a default route (something like “ip
route 0.0.0.0 0.0.0.0 “) pointing to the ISP router.
If no metric is specified, OSPF puts a default value of 20 when redistributing routes from all
protocols except BGP routes (BGP routes get a metric of 1). We use ISP DEF as a backup so its
metric value should be set to a higher value than 20.
There are two types of external routes: external type 1 and external type 2. The difference
between the two is in the way the cost (metric) of the route is being calculated: + The cost of a
type 2 route is always the external cost, irrespective of the interior cost to reach that route. + Type
1 cost is the addition of the external cost and the internal cost used to reach that route.
-> We should configure the type 2 external route to make sure the ISP ABC is always referred
over ISP DEF because internal routing does not determine the path.
Note: E2 is the default external metric, but E1 is preferred over E2 if two equal-cost paths exist.