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QID:N2C33 - Is this a stub router or an ABR - Printable Version

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QID:N2C33 - Is this a stub router or an ABR - joshuad31 - 03-25-2010

Hello,

Please consider the following:
Stub area?This is an area that will not accept external summary routes (Type 5s). Type 5 LSAs are replaced by the ABR with a default route, and internal routers send external traffic to the closest ABR. Stub areas are useful because they protect slower or less powerful routers from being overwhelmed with routes from outside.

Do you see a default route injected by an ABR into this routing table, because I certainly don't.  All stubs must have a default route injected into the area by the ABR.  There isn't a default route; there is a gateway of last resort but the next hop of the gateway is not in the routing table.  This makes this router an ABR.

Please correct.  Thanks!!!

EXHIBIT:
Router# show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default

Gateway of last resort is 30.64.0.2 to network 0.0.0.0

30.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O IA    30.2.0.0/16 [110/74] via 30.64.0.2, 00:09:13, Ethernet0
C        30.1.3.0/24 is directly connected, Serial0
O IA    30.3.0.0/16 [110/148] via 30.64.0.2, 00:05:22, Ethernet0
C        30.1.2.0/24 is directly connected, Serial1

(QID:N2C33) Consider the output of a show ip route command shown in the exhibit. Which two statements about the routing table are true? (Choose two)

The area is a stub.
The area is totally stubby.
Network 30 is using VLSM.
The routing table is for an ABR.

Correct Answer: The area is a stub.
                          Network 30 is using VLSM.
Explanation:
Inter-area summary routes (O IA) are included in the routing table, therefore, it is not a Totally Stubby Area, it is a Stub Area.

The statement, "30.0.0.0/8 is variably subnetted, 9 subnets, 2 masks", shows that network 30 is using VLSM. VLSM means a network can be variably subnetted into smaller networks, where each smaller network can have a different subnet mask.


Re: QID:N2C33 - Is this a stub router or an ABR - joshuad31 - 05-20-2010

Admin I would like a reply on this post