A network administrator recently redistributed RIP routes into an OSPF domain. However,
the administrator wants to configure the network so that instead of 32 external type-5 LSAs
flooding into the OSPF network, there is only one.
What must the administrator do to accomplish this?
A.
Configure summarization on R1 with area 1 range 172.16.32.0 255.255.224.0
B.
Configure summarization on R1 with summary-address 172.16.32.0 255.255.224.0
C.
Configure area 1 as a stub area with area 1 stub
D.
Configure area 1 as a NSSA area with area 1 stub nssa
Explanation:
In many cases, the router doesn’t even need specific routes to each and every subnet (for
example, 172.16.1.0/24). It would be just as happy if it knew how to get to the major network
(for example, 172.16.0.0/16) and let another router take it from there. In our telephone
network example, the local telephone switch should only need to know to route a phone call
to the switch for the called area code. Similarly, a router’s ability to take a group of
subnetworks and summarize them as one network (in other words, one advertisement) is
called route summarization.
Besides reducing the number of routing entries that a router must keep track of, route
summarization can also help protect an external router from making multiple changes to its
routing table due to instability within a particular subnet. For example, let’s say that we were
working on a router that connected to 172.16.2.0/24. As we were working on the router, we
rebooted it several times. If we were not summarizing our routes, an external router would
see each time 172.16.2.0/24 went away and came back. Each time, it would have to modify
its own routing table. However, if our external router were receiving only a summary route
(i.e., 172.16.0.0/16), then it wouldn’t have to be concerned with our work on one particular
subnet. This is especially a problem for EIGRP, which can create stuck in active (SIA) routes
that can lead to a network melt-down.
Summarization Example
We have the following networks that we want to advertise as a single summary route:
* 172.16.100.0/24
* 172.16.101.0/24
* 172.16.102.0/24
* 172.16.103.0/24
* 172.16.104.0/24
* 172.16.105.0/24
* 172.16.106.0/24
Hmm, please explain why A is not the correct answer despite the correct command is “area x range x.x.x.x y.y.y.y”
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I guess the summarization doesnt have to do with areas on R1. Moreover, We are summarizing the routes on the other interface( not on Area1 side).
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The networks are being covered by RIPv2, so I’m guessing you would manually summarize with RIP and then redistribute into OSPF.
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