2013 Latest Cisco 350-001 Exam Section 1: OSPF (20 Questions)
QUESTION NO: 1
Router TK1 is configured for OSPF. Under the OSPF process, you type in the “area
1 range” command. Which LSA types will be acted upon (summarized) as a result?
(Choose all that apply)
A. Type 1
B. Type 2
C. Type 3
D. Type 4
E. Type 5
Answer: A, B
Area range command is used for summarizing routes on the boundary of two OSPF areas.
The information to be summarized is contained in two types of LSAs: Type 1 and Type2.
Type 1 LSAs are Router LSAs and are generated by each router in an OSPF network.
Type 2 LSAs are network LSAs, which are generated by the DR.
Both Type1 and Type 2 LSAs are flooded within the originating area only. Only when the
information needs to be conveyed to another area in a summarized form area-range
command is used, which acts on the information provided by these two LSAs.
CCIE Professional Development Routing TCP/IP Volume I by Jeff Doyle page 471.
C. Type 3 LSA are the result of type 1 and type 2 summaries that are created by the area range command.
D. Type 4 LSAs are ASBR summary LSAs
E. Type 5 LSAs are AS External LSAs
QUESTION NO: 2 A change in the topology of the Testking OSPF network causes the flooding operation. Which OSPF packet types are used in this LSA Flooding?
B. Link State Update
C. Link State Request
D. Database description
E. Link State Acknowledgement
Answer: B, E
A change in the OSPF network topology is represented as a change in one or more of the OSPF Link State Advertisements (LSAs). Flooding is the process by which changed or new LSAs are sent throughout the network, and are used to ensure that the database of every OSPF router is updated and an identical database is maintained. This flooding makes use of two OSPF packet types: Link State Update packets (type 4), and Link State Acknowledgement packets (type 5). Reference: Jeff Doyle, “Routing TCP/IP volume 1” page 451.
QUESTION NO: 3
Router TK1 is configured for OSPF and is connected to two areas: area 0 and area 1. You then configure area 1 as a stub area. Which LSAs will now operate inside of area 1?
A. Type 7
B. Type 1 and 2
C. Type 1, 2, and 5
D. Type 3 and 4
E. Type 1, 2 and 3
Only type 1, 2, and 3 LSAs will be allowed inside of a stub area. Incorrect Answers:
A. Type 7 LSAs are used for NSSA, not stubby areas.
B. Network Summary LSAs (Type 3) are also allowed.
CCIE Professional Development Routing TCP/IP Volume I by Jeff Doyle page 479.
QUESTION NO: 4
Study the Exhibits below carefully:
The following exhibit is an illustration of the output from an ASBR:
ASBBR#show ip ospf database external
OSPF Router with ID (126.96.36.199) (Process ID 10)
Type-5 AS External Link States
LS age: 15
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 10.10.1.0 (External Network Number)
Advertising Router: 188.8.131.52
LS Seq Number: 80000002
Network Mask: /24
Metric Type: 1 (Comparable directly to link state metric)
Forward Address: 0.0.0.0
External Route Tag: 0
And this exhibit is an illustration from a router in the network:
RouterTK1#show ip ospf border-routers
OSPF Process 10 internal Routing Table
Codes: i-intra-area route, I-Inter-area route
184.108.40.206(2) via 220.127.116.11, Serial0/0, ASBR, Area0, SPF 4
Based on this information what is the total metric for the route to subnet 10.10.1.0/24 on Router TK1?
The metric of the external link shows 10. Then we need to add 2 from the inter-area metric, for a total of 12.
QUESTION NO: 5
In your OSPF network serial 0 on your router, TK1, is in area 1. Later, you configure serial 0 as passive. What is the effect of this configuration change?
A. OSPF will accept the routing updates from neighbors.
B. OSPF will form all the available adjacencies out of that interface.
C. OSPF will not insert any of the learned routes in the local routing table.
D. OSPF will not form any adjacency out of that interface.
E. None of the above.
With passive-interface, an adjacency will never occur out of that interface, as no hello
packets are exchanged out of a passive interface.
A. Normally, defining an interface as passive will accomplish this. No routes will be sent out, but routes can still be received. OSPF differs because link state protocols need information for the entire network topology. Defining an interface as passive with OSPF means that the adjacency will not be established, therefore, no routes will be able to be received on that interface.
QUESTION NO: 6 You are the network administrator at TestKing. The TestKing network contains four Routers named TK1, TK2, TK3, and TK4. All four routers are connected to a hub via Ethernet interfaces. All four routers have a basic OSPF configuration of a network statement for the Ethernet network. During routine maintenance, you issue theshow ip ospf neighbor command on Router TK2. The output from the show ip ospf neighbor command shows 2WAY/DROTHER for its neighbor, Router TK3. What conclusions can you draw from this output? (Choose all that apply)
A. Router TK2 is the DR or BDR.
B. Router TK3 is not a DR or BDR.
C. Router TK2 – Router TK3 adjacency is not yet FULL.
D. Router TK2 is not the DR.
E. Router TK4 is the DR.
Answer: B, D
OSPF routers can have one of three neighbor relationships: Designated Router (DR),
Backup Designated Router (BDR), or neither. For neither, the router neighbor
relationship will show as 2WAY/DROTHER.
A, C. 2WAY/DROTHER means that the two routers are neither the DR nor the BDR.
E. Either Router TK1 or Router TK4 is the DR. Based on the information that is provided we cannot be sure which one it is.
QUESTION NO: 7
The following exhibit displays the Testking OSPF network:
Router TK2 needs to send a string of packets to router TK4. How will router TK2 decide the path to take to reach TK4?
A. TK2 will select a path after considering the costs inside Area 1 only.
B. TK2 will alternate between Router TK1 and Router TK3 if the costs are equal.
C. TK 2 will always go through Router TK1 with no regard for costs.
D. TK2 will select a path after considering the costs inside both Area 0 and Area 1.
E. None of the above.
OSPF prefers Intra Area Path over Inter Area Paths.
B. The Answer B is incorrect because OSPF does not conduct ECMP load balancing on multiple paths with equal cost if the respective paths span through more than one area. B is incorrect for several reasons. If a packet has to alternate between two paths that means Per Packet load balancing is in effect. Which is normally in place for links less than 56k. For higher link speeds fast switching (default switching mode) is enabled. In this mode all packets to one destination in a target subnet are sent over one path, since route lookup is not performed for every packet, it is rather performed per flow. So B is totally ruled out.
C. Even though router TK1 is the most direct way to reach area 0, OSPF will always prefer to stay in the same area over traversing multiple areas.
D. OSPF prefers Intra area paths, so only the costs associated with reaching TK4 via area 1 will be considered first.
QUESTION NO: 8 Router TK1 is configured for OSPF. Interface serial 0 is configured to be in area 0 and interface serial 1 is configured to be in area 1. Under the OSPF process “area 1 nssa default-information-originate” is configured. Which of the following are true? (Choose all that apply)
A. TK1 will inject a type 3 default route into area 1.
B. TK1 will inject a type 7 default route into area 1.
C. TK1 will inject a type 7 default route into area 0.
D. TK1needs a default route in its routing table to inject a default into area 1.
E. TK1 does not need a default route in its routing table to inject a default into area 1.
Answer: B, D
Type 7 routes are injected into OSPF NSSA areas, and the default information originate command will make TK1 inject type 7 default routes into area 1. As a rule, an OSPF router will need a default route itself before injecting a default route into an area, unless the keyword “always” is used in the configuration. For example, “default-information originate always.”
A. In a NSSA area, the NSSA area generates the default route with the “default-information originate” command, but unlike other default routes that use type 3 information, NSSA default routes use type 7.
C. TK1 will inject a type 7 NSSA route into area 1, not area 0. Area 0 can not be an NSSA.
E. Using the command shown in the question above will not create the route, because a previous default route did not already exist within the routing table. A default route would have been injected only if the keyword “always” was inserted.
QUESTION NO: 9
Which of the following OSPF routers can generate a type 4 ASBR-summary LSA?
(Choose all that apply)
Type 4 LSAs are only put out by ABRs and only in two cases: 1. There is an ASBR that the ABR needs to tell the backbone area about. 2. There is a legacy router that is incapable of demand circuits. These last two are indication LSAs and are put out only by an ABR putting itself in the ASBR position, but it is still not an ASBR. An ASBR would not be responsible for reporting either of these situations.
QUESTION NO: 10
Routers TK1 and TK2 are in the same LAN and both are running OSPF. Which multicast IP address will TK1 and TK2 use for sending routing updates to each other? (Choose all that apply)
Answer: D, F
18.104.22.168 is the all-OSPF routers multicast and 22.214.171.124 is the Designated Routers
A. 126.96.36.199 is used for IGRP.
B. 188.8.131.52 is reserved for all systems on the subnet.
D. 184.108.40.206 is used by PIM.
E. 220.127.116.11 is reserved for RIP version 2 announcements.
QUESTION NO: 11 The Testking WAN utilizes OSPF as shown below. The OSPF metric for each link is displayed in the diagram as follows: What is the OSPF shortest path from Network 2 to Network 1 with the OSPF link costs shown in the exhibit?
A. H G D B A
B. H G E C B A
C. H G F D B A
D. H G E D B A
Cost of links from Network 2 to Network 1 is:
A. H G D B A = 1+1 +5 +48 +10 = 65
B. H G E C B A = 1+1+1+30+1+10= 44
C. H G F D B A = 1+1+10+48+48+10= 118
D. H GE D B A = 1+1+1+10+48+10= 71
Therefore, the shortest path is the lowest cost path which is option B. It is important to remember that OSPF uses the total cost of the metrics from a source to a given destination, and the number of hop counts is irrelevant.
QUESTION NO: 12 The Testking router TK2 is experiencing OSPF problems with a neighbor across a frame relay network. During troubleshooting, OSPF event debugging was issued as shown below:
TK2#debug ip ospf events
OSPF events debugging is on
OSPF: Rcd hello from 192.168.0.6 area 4 from
Ethernet 0/0 18.104.22.168
OSPF: End of hello processing
OSPF: Send hello to 244.0.0.5 area 4 on
Ethernet0/0 from 22.214.171.124
OSPF: Rcd hello from 192.168.0.3 area 3 from
OSPF: Mismatched hello parameters from
00:16:28: OSPF: Dead R 40 C 120, Hello R 10 C 30 Mask R
255.255.255.252 C 255.255.255.252
OSPF: Rcd hello from 192.168.0.6 area 4 from
OSPF: End of hello processing
OSPF: Send hello to 126.96.36.199 area 4 on
Ethernet0/0 from 188.8.131.52
Based on the information above, what is the most likely reason for the OSPF problems across the frame relay link?
A. This router is in area 4 while its neighbor is configured to be in area 3.
B. There is mismatch between the OSPF frame-relay parameters configured on this router and those configured on its neighbor.
C. The OSPF network mode configured on this router is not the same as the mode configured on its neighbor.
D. This router has a frame-relay interface DLCI statement that is using the broadcast mode. While its neighbor is using a point-to-point mode.
E. None of the above.
The default timers for a broadcast network (LAN) are: Hello 10 seconds, Dead 40 seconds The default timers for an NBMA network (Frame Relay) are: Hello 30 seconds, Dead 120 seconds. The problem above shows that these timers do not match at each end. The “Dead R 40 C 120, Hello R 10 C 30” means that the configured Dead time is 120 seconds locally on this router, but the received update shows it is configured to be 40 seconds. Similarly, the received hello packet shows that it has a hello time of 10 seconds, where router TK2 is configured for 30 seconds. Although the remote router may have had their timers changed manually within the OSPF process, the most likely cause of the problem is that router TK2 is configured with a network type of NBMA and the other router is configured with a network type of broadcast.
A. It is common for a router with multiple interfaces to be in different OSPF areas. Each network link must be in the same area, but each router can have multiple interfaces, that each belongs to a different area.
B. The Frame relay parameters do not appear to be misconfigured, just the OSPF timer values.
D. The timers on the local router, TK2, is 30 seconds for the Hello and 120 seconds for the dead, so this router is configured with a NBMA or pt-pt type, while the remote router is using a broadcast network type.
QUESTION NO: 13 Which of the following statements are true regarding the SPF calculation? (Select three)
A. The Dijkstra algorithm is run two times.
B. The previous routing table is saved.
C. The present routing table is invalidated.
D. A router calculates the shortest-path cost using their neighbor(s) as the root for the SPF tree.
E. Cisco routers use a default OSPF cost of 10^7/BW.
Answer: A, B, C
The Dijkstra algorithm code itself is run two times. The first time deals with routers and the second time always deals with networks. When the Shortest Path First (SPF) algorithm is computed by an OSPF router, the previous routing table is save before the calculation and used in case any problems arise with the new one. It then invalidates the present routing table and performs the calculation using ITSELF as root in the SPF tree.
D. The router itself is the root, not the neighbor. A router periodically advertises its status or link state to its adjacencies. Link state advertisements flood throughout an area ensuring that all routers have exactly the same topological database. This database is a collection of the link state advertisements received from each router belonging to an area. From the information in this database, each router can calculate a shortest path tree with itself designated as the root of the tree.
E. The default OSPF cost of any link is 10^8/Bandwidth, or 100,000,000/BW.
QUESTION NO: 14
The TestKing network is displayed below:
Given the network and OSPF configuration shown above, what statement is true regarding traffic flowing from PC-TestKingA to PC-TestKingB?
A. Traffic will only flow on the shortest, low-speed path, PC-TestKingA – TestKing8 -TestKing4 – TestKing 2- TestKing1 – PC-TestKingB.
B. Traffic will flow on both the high speed paths (PC- TestKingA – TestKing8 – TestKing 6- TestKing3 – TestKing2 – TestKing1 – PC- TestKingB and PC- TestKingA – TestKing8
– TestKing7 – TestKing5 – TestKing2 – TestKing1 – PC- TestKingB) but not the
C. Traffic will flow on all three of the paths.
D. Traffic will flow uni-directionally on one of the high-speed paths from PC- TestKingA to PC- TestKingB, and uni-directionally on one of the high speed paths from PC-TestKingB o PC- TestKingA.
E. Traffic will flow bi-directionally on only one of the high-speed paths, and the path selected will be based on the OSPF process IDs.
OSPF uses the bandwidth of the links for the metric, and by default the 100 Mbps links will have an OSPF metric of 1 while the low speed links will have a metric of 10 so only the high speed Ethernet links will be used. By default, OSPF load balances on up to four equal cost paths. Since both high speed paths will have a metric of 3 (1+1+1) from router TestKing8 to TestKing2 they traffic will load balance over the two paths.
QUESTION NO: 15 What statement is correct regarding OSPF adjacencies and link-state database synchronization?
A. Full adjacency occurs when OSPF routers reach the LOADING state.
B. Adjacency relationship begins in the EXSTART state.
C. All OSPF neighbors establish adjacencies in the FULL state with all other routers on the broadcast network.
D. The INIT state indicates that a router has received a Hello packet from a neighbor and has seen their own ROUTERID in the Hello packet.
The various states in which a neighbor can be are discussed below.
Down – the initial state of a neighbor conversation.
Attempt – indicates that an attempt should be made to contact the neighbor.
Init – hello packet has been received from the neighbor.
2-Way – communication between two routers is bi-directional.
ExStart -first step to creating an adjacency between the two neighboring routers.
Exchange – the router is sending data description packets to the neighbor.
Loading – Link state request packets are sent to the neighbor.
Full – the neighboring routers are fully adjacent.
A. Full adjacency only occurs after the OSPF router has reached a FULL state.
C. In a broadcast network, all routers only become adjacent with the Designated Router (DR).
D. This state specifies that the router has received a hello packet from its neighbor, but the receiving router’s ID was not included in the hello packet. When a router receives a hello packet from a neighbor, it should list the sender’s router ID in its hello packet as an acknowledgment that it received a valid hello packet.
QUESTION NO: 16 OSPF is running on the TestKing network. In OSPF, what LSA type would only cause a partial SPF calculation?
A. Type 1
B. Type 2
C. Type 4
D. Type 7
E. Type 9
OSPF Type 7 LSA’s are reserved for Not So Stubby Areas (NSSA). This area accepts Type 7 LSAs which are external route advertisements like Type 5s but they are only flooded within the NSSA. This is usually used when connecting to a branch office running an IGP. Normally this would have to be a standard area since a stub area would not import the external routes. If it was a standard area linking the ISP to the branch office then the ISP would receive all the Type 5 LSAs from the branch which it does not want. Because Type 7 LSAs are only flooded to the NSSA the ISP is saved from the external routes whereas the NSSA can still receive them. Therefore, when this LSA is generated, only a partial SPF calculation needs to be performed.
QUESTION NO: 17 OSPF is being used as the routing protocol in the TestKing network. Which two statements regarding the SPF calculation on these OSPF routers are true? (Select two)
A. The existing routing table is saved so that changes in routing table entries can be identified.
B. The present routing table is invalidated and is built again from scratch.
C. The Cisco router calculates the shortest-path cost using their neighbor(s) as the root for the SPF tree.
D. Cisco routers use a default OSPF cost of 10^7/BW.
Answer: A, B
When an OSPF router performs a new SPF calculation, the existing routing table is saved and used as a baseline for changes made to the network topology. When any SPF calculation is made, the OSPF neighbor or neighbors is used as the root of the SPF routing tree.
C. The root of the SPF tree is always the router itself, not the neighboring router.
D. The default cost for all OSPF links is 10^8/BW, or 100,000,000/ configured bandwidth.
QUESTION NO: 18
The TestKing OSPF/RIPv2 network is displayed below:
Area 1 is an OSPF Not So Stubby Area (NSSA). What type of LSA will TestKing3 send out area 0 to indicate the presence of an ASBR in Area 1?
A. A type 5 because P-bit has been set in the type 4 LSA that was sent from TestKing1 to TestKing3.
B. A type 4 because the E-bit was set in the type 7 LSA that was sent from TestKing1 to TestKing3.
C. A type 1 because the B-bit was set in the LSA that was propagated from TestKing1 to TestKing3.
D. A type 3 because the E-bit was set in the type 1 LSA that was sent from TestKing1 to TestKing3.
In this case a type 5 LSA would be sent by the ASBR, which is TestKing1. Type 5 Link State advertisements are generated by the ASBR and describe links external to the Autonomous System (AS). This LSAS is flooded to all areas except stub areas. Here TestKing1 is considered to be an ASBR since it is directly connected with the RIP version 2 network. The E-bit reflects the associated area’s External Routing Capability. AS external link advertisements are not flooded into/through OSPF stub areas. The E-bit ensures that all members of a stub area agree on that area’s configuration. LSA type 3 and 4 are summary link advertisements generated by ABRs describing inter-area routes. Type 3 describes routes to networks and is used for summarization. Type 4 describes routes to the ASBR. Since TestKing3 needs to advertise the presence of an ASBR, it will send out a type 4 LSA to area 0. Reference:http://www.cisco.com/warp/public/104/ospfdb6.html
QUESTION NO: 19
What statement is accurate regarding OSPF areas?
A. Redistribution is allowed into all types of OSPF areas.
B. When routes are redistributed into an OSPF stub area, they enter as type-5 LSAs.
C. Redistribution is allowed into an OSPF stub area, but not into an OSPF not-so-stubby area.
D. When routes are redistributed into an OSPF not-so-stubby area, they enter as type-5 LSAs.
E. When routes are redistributed into an OSPF not-so-stubby area, they enter as type-7 LSAs.
When routes are redistributed into OSPF, these routes are considered to be external routes. External LSAs are type 5 LSAs. Not so stubby areas allow external routes to be advertised into OSPF network while retaining the charactersistics of a stub area. To do this, the ASBR (the one doing the redistributing) in the NSSA will originate a type 7 LSA to advertise the external destinations. Reference: Jeff Doyle, Routing TCP/IP volume 1, page 483. Incorrect Answers:
A. Type 5 LSAs are only allowed into Backbone (area 0) and non backbone, non-stub areas.
B. Type 5 LSAs (external LSAs) are not allowed into stub or totally stub areas.
C. The opposite is true. External LSAs are allowed into NSSA, but not stub areas.
D. Type 5 LSAs are not inserted into NSSA for external routes. Type 7 LSAs are created for this purpose.
QUESTION NO: 20 Within the TestKing OSPF network, which statement is true regarding the LSA’s contained in the link state database? (Choose all that apply).
A. The LSRefreshTime is 30 minutes.
B. LSA’s can only be reflooded by the router that originated the LSA.
C. When an LSA reaches its MaxAge the router will send out a purge message to the other routers within its area.
D. All LSAs contained in the LSDB expire at the same time unless they are refreshed.
E. The MaxAge of an LSA is 3600 seconds.
Answer: A, E
Each OSPF LSA has an age, which indicates whether the LSA is still valid. Once the LSA reaches the maximum age (one hour), it is discarded. During the aging process, the originating router sends a refresh packet every 30 minutes to refresh the LSA. Refresh packets are sent to keep the LSA from expiring, whether there has been a change in the network topology or not. Checksumming is performed on all LSAs every 10 minutes. The router keeps track of LSAs it generates and LSAs it receives from other routers. The
B. Each LSA gets refreshed when it is 30minutes old, independent of the other LSAs used by other OSPF routers.
C. Purge messages are not sent to neighboring routers since each router uses its own timers.
D. Global synchronization can be problematic in OSPF networks. This problem is solved by each LSA having its own timer. Each LSA gets refreshed when it is 30minutes old, independent of other LSAs, so the CPU is used only when necessary.
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