Which of the following are true regarding OSPF areas?
You must have separate loopback interfaces configured in each area.
The numbers you can assign an area go up to 65,535.
The backbone area is also called area 0.
If your design is hierarchical, then you don't need multiple areas.
All areas must connect to area 0.
Options
A. 1 only
B. 1 and 2 only
C. 3 and 4 only
D. 3, 4 and 5
Correct Answer
3, 4 and 5
Explanation
Loopback interfaces are created on a router, and the highest IP address on a loopback (logical) interface becomes the RID of the router but has nothing to do with areas and is optional, so (1) is wrong. The numbers you can create an area with are from 0 to 4,294,967,295 option (2) is wrong. The backbone area is called area 0, so option (3) is correct. All areas must connect to area 0, so option (5) is correct. If you have only one area, it must be called area 0. This leaves option (4), which must be correct; it doesn't make much sense, but it is the best answer.
EIGRP and OSPF problems
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1. If routers in a single area are configured with the same priority value, what value does a router use for the OSPF Router ID in the absence of a loopback interface?
Options
A. The lowest IP address of any physical interface
B. The highest IP address of any physical interface
C. The lowest IP address of any logical interface
D. The highest IP address of any logical interface
Correct Answer: The highest IP address of any physical interface
Explanation:
At the moment of OSPF process startup, the highest IP address on any active interface will be the Router ID (RID) of the router. If you have a loopback interface configured (logical interface), then that will override the interface IP address and become the RID of the router automatically.
2. A network administrator needs to configure a router with a distance-vector protocol that allows classless routing. Which of the following satisfies those requirements?
In this question, we're calling EIGRP just plain old distance vector. EIGRP is an "advanced" distance-vector routing protocol, sometimes called a hybrid routing protocol because it uses the characteristics of both distance-vector and link-state routing protocols.
3. Which two of the following commands will place network 10.2.3.0/24 into area 0?
To enable OSPF, you must first start OSPF using a Process ID. The number is irrelevant; just choose a number from 1 to 65,535 and you're good to go. After you start the OSPF process, you must configure any network that you want advertised via OSPF using wildcards and the area command. Statement (4) is wrong because there must be a space after the parameter area and before you list the area number.
4. Your company is running IGRP using an AS of 10. You want to configure EIGRP on the network but want to migrate slowly to EIGRP and don't want to configure redistribution. What command would allow you to migrate over time to EIGRP without configuring redistribution?
If you enable EIGRP on a router with the same autonomous system (AS) number, EIGRP will automatically redistribute IGRP into EIGRP. You will see the IGRP injected routes as external (EX) routes with an EIGRP AD of 170. This is a nice feature that lets you migrate slowly to EIGRP with no extra configuration.
5. Which EIGRP information is held in RAM and maintained through the use of Hello and update packets?
EIGRP holds three tables in RAM: neighbor, topology, and routing. The neighbor and topology tables are built and maintained with the use of Hello packets.
6. Which of the following describe the process identifier that is used to run OSPF on a router?
It is locally significant.
It is globally significant.
It is needed to identify a unique instance of an OSPF database.
It is an optional parameter required only if multiple OSPF processes are running on the router.
The Process ID for OSPF on a router is only locally significant and you can use the same number on each router, or each router can have a different number-it just doesn't matter. The numbers you can use are from 1 to 65,535. Don't get this confused with area numbers, which can be from 0 to 4.2 billion.
7. Which type of OSPF network will elect a backup designated router?
DR and BDR are elected on broadcast and non-broadcast multi-access networks. Frame Relay is a non-broadcast multi-access (NBMA) network by default. No DR is assigned on any type of point-to-point link. No DR/BDR is assigned on the NBMA point-to-multipoint due to the hub/spoke topology.
Correct Answer: In the routing table and the topology table
Explanation:
Successor routes are going to be in the routing table since they are the best path to a remote network. However, the topology table has a link to each and every network, so the best answer is topology table and routing table. Any secondary route to a remote network is considered a feasible successor, and those routes are only found in the topology table and used as backup routes in case of primary route failure.
9. What are reasons for creating OSPF in a hierarchical design?
To decrease routing overhead
To speed up convergence
To confine network instability to single areas of the network
OSPF is created in a hierarchical design, not a flat design like RIP. This decreases routing overhead, speeds up convergence, and confines network instability to a single area of the network.
10. Which is true regarding EIGRP successor routes?
A successor route is used by EIGRP to forward traffic to a destination.
Successor routes are saved in the topology table to be used if the primary route fails.
Successor routes are flagged as "active" in the routing table.
A successor route may be backed up by a feasible successor route.
Successor routes are stored in the neighbor table following the discovery process.
Successor routes are the routes picked from the topology table as the best route to a remote network, so these are the routes that IP uses in the routing table to forward traffic to a remote destination. The topology table contains any route that is not as good as the successor route and is considered a feasible successor, or backup route. Remember that all routes are in the topology table, even successor routes.