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QUESTION 1
Which address type does the IPv6 address FF05:0:0:0:0:0:0:2 specify?
A. unspecified
B. aggregable global unicast
C. link local
D. site local unicast
E. multicast
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Explanation: All IPv6 multicast addresses start with the first 8 bits of the address set to 1. Thus all multicast addresses start with the hexadecimal notation FF (1111 1111). The multicast range is as follows: FF00::/8 FFFF::/8 The second octet, following to the first octet of FF, identifies both the scope and the lifetime of the multicast address. In this way, IPv6 has millions of group multicast addresses to use in current and emerging technologies. Reference: CCNP Self-Study CCNP BSCI Exam Certification Guide p.112
QUESTION 2
In IS-IS routing, which level is used to route between different areas within the same domain?
A. Level 0
B. Level 1
C. Level 2
D. Level 3
Correct Answer: C Section: (none) Explanation
QUESTION 3
Exhibit, Network Topology You work as a network technician at Certkiller .com. Study the exhibits carefully. Which statement is true about the Certkiller .com network?
A. There is a match entry missing in the route-map REDIST-MAP permit 30 statement.
B. All routes not matching access list 101 or 110 will be flagged as an OSPF external type 2 with a metric of 5000.
C. There is a set entry missing in the route-map REDIST-MAP deny 20 statement.
D. All routes matching access list 110 will be forwarded.
E. The set metric-type entry is not a valid route-map command.
Correct Answer: B Section: (none) Explanation
QUESTION 4
Exhibit, Network topology You work as a network technician at Certkiller .com. Study the exhibits carefully. If the following command, default information-originate, is added to the OSPF configuration on Certkiller 1, what will the neighboring routers see in their route table?
A. S* 0.0.0.0/0 [1/0] via 6.0.0.3, 00:28:00
B. O E1 0.0.0.0 [1/0] via 6.0.0.3, 00:28:00
C. O E2 0.0.0.0 [1/0] via 6.0.0.3, 00:28:00
D. No default routes will be propagated to neighboring routers.
Correct Answer: D Section: (none) Explanation
QUESTION 5
Exhibit, Network Topology You work as a network technician at Certkiller .com. Study the exhibits carefully. If the following command, variance 3, were added to Certkiller 5, which path or paths would be chosen to route traffic from Certkiller 5 to network X?
A. Certkiller 5- Certkiller 2- Certkiller 1
B. Certkiller 5- Certkiller 2- Certkiller 1 and Certkiller 5- Certkiller 3- Certkiller 1.
C. Certkiller 5- Certkiller 3- Certkiller A and Certkiller 5- Certkiller 4- Certkiller 1.
D. Certkiller 5- Certkiller 2- Certkiller 1, Certkiller 5- Certkiller 3- Certkiller 1, and Certkiller 5- Certkiller 4-Certkiller 1.
Correct Answer: C Section: (none) Explanation
QUESTION 6
Exhibit, Network Topology
You work as a network technician at Certkiller .com. Study the exhibits carefully. Both Certkiller 5 and Certkiller 2 are performing two-way IGRP/RIP route redistribution. What behavior will Certkiller 2 use with the given Certkiller 2 configurations?
A. Updates about 192.168.1.0 that are learned through RIP will be ignored.
B. Updates about 192.168.1.0 will be advertised out the s0 interface.
C. Updates about 192.168.1.0 that are heard through the s1 interface will be ignored.
D. Updates about 192.168.1.0 that are learned through IGRP will be added to the routing table, but not advertised to Certkiller 1.
Correct Answer: C Section: (none) Explanation
QUESTION 7
Exhibit, Network Topology You work as a network technician at Certkiller .com. Study the exhibits carefully. Which command will Certkiller 2 use to summarize routes for the 192.168.16.0/22 supernet before injecting them into Area 0?
A. area 10 range 192.168.16.0 255.255.252.0
B. summary-address 192.168.16.0 255.255.252.0
C. ip summary-address ospf 101.192.168.16.0 255.255.252.0
D. area 0 range 192.168.16.0 255.255.252.0
E. ip summary-address area 0 192.168.16.0 255.255.252.0
Correct Answer: A Section: (none) Explanation
QUESTION 8
Which three are advantages to creating multiple areas in OSPF? Select three.
A. less frequent SPF calculations
B. fewer hello packets
C. smaller routing tables
D. reduced LSU overhead
E. fewer adjacencies needed
Correct Answer: ACD Section: (none) Explanation
QUESTION 9
Exhibit, Network Topology
You work as a network technician at Certkiller .com. Study the exhibits carefully. If the following command, variance 2, were added to Certkiller 5, which path or paths would be chosen to route traffic from Certkiller 5 to network X?
A. Only Certkiller 5- Certkiller 4- Certkiller 1
B. Only Certkiller 5- Certkiller 2- Certkiller 1
C. Only Certkiller 5- Certkiller 3- Certkiller 1
D. Both Certkiller 5- Certkiller 2- Certkiller 1 and Certkiller 5- Certkiller 3- Certkiller 1
E. Both Certkiller 5- Certkiller 2- Certkiller 1 and Certkiller 5- Certkiller 4- Certkiller 1
F. All available paths.
Correct Answer: D Section: (none) Explanation
QUESTION 10
Exhibit interface serial0 bandwidth 40 ip bandwidth-percent eigpr 1 200 In the configuration in the exhibit, how much bandwidth will be used by the EIGRP updates?
A. 40 kbps
B. 60 kbps
C. 80 kbps
D. 200 kbps
E. 40 Mbps
F. 60 Mbps
G. 80 Mbps
H. 200 Mbps
Correct Answer: C Section: (none) Explanation
QUESTION 11
Which statement is true about EBGP?
A. An internal routing protocol can be used to reach an EBGP neighbor?
B. The next hop does not change when BGP updates are exchanged between EBGP neighbors.
C. A static route can be used to form an adjacency between neighbors.
D. EBGP requires a full mesh.
Correct Answer: C Section: (none) Explanation
QUESTION 12
Which three are characteristics of IPv6? Select three.
A. An IPv6 address is 128 bits long.
B. An IPv6 address is 20 bits long.
C. An IPv6 header contains the next header field.
D. An IPv6 header contains the protocol field.
E. IPv6 routers send RA messages.
F. An IPv6 header contains the header checksum field.
Correct Answer: ACE Section: (none) Explanation QUESTION 13
Which three techniques can be used to transition from IPv4 to IPv6? Select three.
A. 6to4 tunneling
B. flow label
C. dual stack
D. anycast
E. NAT
F. mobile IP
Correct Answer: AD Section: (none) Explanation
QUESTION 14
Exhibit, Network Topology
Exhibit You work as a network technician at Certkiller .com. Studyy the exhibit carefully. What is the effect of the distribute list command in the Certkiller 1 configuration?
A. Certkiller 1 will filter only the 172.24.1.0/24 route from the Certkiller 2 RIP updates.
B. Certkiller 1 will permit only the 10.0.0.0/24 route in the Certkiller 2 RIP updates.
C. Certkiller 1 will filter 10.1.0.0/24 and the 172.24.1.0/24 routes from the Certkiller 2 RIP updates.
D. Certkiller 1 will not filter any routes because there is no exact prefix match.
Correct Answer: C Section: (none) Explanation
QUESTION 15
The Certkiller WAN is displayed in the following diagram:
When performing a show run on router Certkiller 1, you notice that two static entries shown above were
configured for the 10.0.0.0 network.
Which path will be selected by the router as the best path?
A. Per-destination load sharing will be implemented.
B. The path through Certkiller 2 will be used.
C. The path through Certkiller 3 will be used.
D. Per-packet load sharing will be implemented.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation: A static route configured using the interface is considered to be a directly connected route. Directly connected
routes have an administrative distance of 0, while all other static routes have and AD of 1. In this case, the route specifying the interface will be chosen over a static route that specifies the IP address of the next hop, because of the lower AD.
QUESTION 16
How many update packets would a RIPv2 router send to advertise 77 routes?
A. one update package
B. two update package
C. three update package
D. four update package
E. five update package
F. six update package
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:
RIP 2 Packet Format:
The RIP 2 specification (described in RFC 1723) allows more information to be included in RIP packets
and provides a simple authentication mechanism that is not supported by RIP. Figure 47-2 shows the IP
RIP 2
packet format.
The following descriptions summarize the IP RIP 2 packet format fields illustrated in Figure 47-2:
1.
Command-Indicates whether the packet is a request or a response. The request asks that a router send all or a part of its routing table. The response can be an unsolicited regular routing update or a reply to a request. Responses contain routing table entries. Multiple RIP packets are used to convey information from large routing tables.
2.
Version-Specifies the RIP version used. In a RIP packet implementing any of the RIP 2 fields or using authentication, this value is set to 2.
3.
Unused-Has a value set to zero.
4.
Address-family identifier (AFI)-Specifies the address family used. RIPv2’s AFI field functions identically to RFC 1058 RIP’s AFI field, with one exception: If the AFI for the first entry in the message is 0xFFFF, the remainder of the entry contains authentication information. Currently, the only authentication type is simple password.
5.
Route tag-Provides a method for distinguishing between internal routes (learned by RIP) and external routes (learned from other protocols).
6.
IP address-Specifies the IP address for the entry.
7.
Subnet mask-Contains the subnet mask for the entry. If this field is zero, no subnet mask has been specified for the entry.
8.
Next hop-Indicates the IP address of the next hop to which packets for the entry should be forwarded.
9.
Metric-Indicates how many internetwork hops (routers) have been traversed in the trip to the destination. This value is between 1 and 15 for a valid route, or 16 for an unreachable route. NoteUp to 25 occurrences of the AFI, Address, and Metric fields are permitted in a single IP RIP packet. That is, up to 25 routing table entries can be listed in a single RIP packet. If the AFI specifies an authenticated message, only 24 routing table entries can be specified. Given that individual table entries aren’t fragmented into multiple packets, RIP does not need a mechanism to resequence datagrams bearing routing table updates from neighboring routers. Since a single update packet can contain at most 25 route entries, 4 packets will be needed to advertise 77 routes.
QUESTION 17
What are three disadvantages of a router-on-stick configuration for InterVLAN routing? (Choose three)
A. InterVLAN routing cannot be filtered by the router.
B. The router becomes a single point of failure for the network.
C. Routers will not route STP BPDUs.
D. There is a possibility of inadequate bandwidth for each VLAN.
E. Additional overhead on the router can occur.
F. NetFlow Switching is required for InterVLAN accounting.
Correct Answer: BDE Section: (none) Explanation
Explanation/Reference:
Explanation:
When a single interface is used to route between subnets or networks, this is know as a router-on-a-stick.
To assign multiple IP addresses to the same interface, secondary addresses or subinterfaces are used.
The Advantage is that it is useful when there are limited Ethernet interfaces on the router.
The Disadvantages to this design are:
subnets. resources that will be consumed on the router can become an issue.
QUESTION 18
What are three characteristics of RIPv2? (Choose three)
A. Supports variable-length subnet mask by default.
B. Does not support variable-length subnet mask by default.
C. Supports discontiguous networks by default.
D. Multicast updates to 224.0.0.9.
E. Broadcast updates.
Correct Answer: ACD Section: (none) Explanation Explanation/Reference:
Explanation: Features of RIP v2 To help today’s IP internetworks minimize broadcast traffic, use variable length subnetting to conserve IP addresses, and secure their routing environment from misconfigured or malicious routers, several key features were added to RIP v2. Multicasted RIP Announcements Rather than broadcasting RIP announcements, RIP v2 supports sending RIP announcements to the IP multicast address of 224.0.0.9. Non-RIP nodes are not disturbed by RIP router announcement traffic. Subnet Masks RIP v2 announcements send the subnet mask (also known as a network mask) along with the network ID. RIP v2 can be used in subnetted, supernetted, and variable-length subnet mask environments. Subnets of a network ID do not have to be contiguous (they can be disjointed subnets).
QUESTION 19
The Bellman-Ford algorithm is used by the grand majority of distance vector routing protocols in DUAL (diffusing update algorithm). Which of the following routing protocols is it?
A. IGRP
B. OSPF
C. EIGRP
D. RIP v.2
E. RIP v.1
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: DUAL is used by EIGRP. The Diffusing Update Algorithm (DUAL) is the algorithm used to obtain loop-freedom at every instant throughout a route computation. This allows all routers involved in a topology change to synchronize at the same time. Routers that are not affected by topology changes are not involved in the recomputation. The DUAL finite state machine embodies the decision process for all route computations. It tracks all routes advertised by all neighbors. The distance information, known as a metric, is used by DUAL to select efficient loop free paths. DUAL selects routes to be inserted into a routing table based on feasible successors. A successor is a neighboring router used for packet forwarding that has a least cost path to a destination that is guaranteed not to be part of a routing loop. When there are no feasible successors but there are neighbors advertising the destination, a recomputation must occur.
QUESTION 20
The Certkiller EIGRP network is displayed in the following topology diagram:
You work as a network technician at Certkiller .com. Study the exhibits carefully. If the command “variance 3” was added to the EIGRP configuration of Certkiller 5, which path or paths would be chosen to route traffic from Certkiller 5 to network X?
A. Certkiller 5- Certkiller 2- Certkiller 1
B. Certkiller 5- Certkiller 2- Certkiller 1 and Certkiller 5- Certkiller 3- Certkiller 1.
C. Certkiller 5- Certkiller 3- Certkiller A and Certkiller 5- Certkiller 4- Certkiller 1.
D. Certkiller 5- Certkiller 2- Certkiller 1, Certkiller 5- Certkiller 3- Certkiller 1, and Certkiller 5- Certkiller 4-Certkiller 1.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: Every routing protocol supports equal cost path load balancing. In addition to that, IGRP and EIGRP also support unequal cost path load balancing. Use the variance command to instruct the router to include routes with a metric less than n times the minimum metric route for that destination, where n is the number specified by the variance command. The variable n can take a value between 1 and 128, with the default being 1, which means equal cost load balancing. Traffic is also distributed among the links with unequal costs, proportionately, with respect to the metric. Reference: http://www.cisco.com/en/US/tech/ CK3 65/technologies_tech_note09186a008009437d.shtml
QUESTION 21
What is the purpose of the “eigrp stub” configuration command?
A. To increase scalability by limiting the EIGRP query range.
B. To reduce the size of the routing table by blocking the D EX (External EIGRP) routes in the EIGRP stub router.
C. To reduce the convergence time by enabling the EIGRP stub router to propagate the EIGRP queries from the EIGRP hub router.
D. To reduce the convergence time by enabling the EIGRP stub router to also perform query requests to the EIGRP hub router.
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation: Complex, redundant EIGRP networks can cause scalability problems. The best solution to this is to provide a means within the context of the EIGRP protocol itself to control traffic flows and limit query depth. TheEIGRP Stub Router functionality in Cisco IOS Software Release 12.0(7)T can achieve this solution. The Enhanced Interior Gateway Routing Protocol (EIGRP) Stub Routing feature improves network stability, reduces resource utilization, and simplifies stub router configuration. Stub routing is commonly used in a hub and spoke network topology. In a hub and spoke network, one or more end (stub) networks are connected to a remote router (the spoke) that is connected to one or more distribution routers (the hub). The remote router is adjacent only to one or more distribution routers. The only route for IP traffic to follow into the remote router is through a distribution router. This type of configuration is commonly used in WAN topologies where the distribution router is directly connected to a WAN. The distribution router can be connected to many more remote routers. Often, the distribution router will be connected to 100 or more remote routers. In a hub and spoke topology, the remote router must forward all nonlocal traffic to a distribution router, so it becomes unnecessary for the remote router to hold a complete routing table. Generally, the distribution router need not send anything more than a default route to the remote router. When using the EIGRP Stub Routing feature, you need to configure the distribution and remote routers to use EIGRP, and to configure only the remote router as a stub. Only specified routes are propagated from the remote (stub) router. The router responds to queries for summaries, connected routes, redistributed static routes, external routes, and internal routes with the message “inaccessible.” A router that is configured as a stub will send a special peer information packet to all neighboring routers to report its status as a stub router. Any neighbor that receives a packet informing it of the stub status will not query the stub router for any routes, and a router that has a stub peer will not query that peer. The stub router will depend on the distribution router to send the proper updates to all peers.
QUESTION 22
The Certkiller OSPF network is displayed below: Refer to the exhibit. All routers have converged and neighbor relationships have been established. Which state is Certkiller 4 in?
A. 2WAY/DROTHER
B. 2WAY/BDR
C. 2WAY/DR
D. FULL/DROTHER
E. FULL/BDR
F. FULL/DR
Correct Answer: F Section: (none) Explanation
Explanation/Reference:
Explanation: The router with the highest OSPF priority on a segment will become the DR for that segment. The same process is repeated for the BDR. In case of a tie, the router with the highest RID will win. The default for the interface OSPF priority is one. Based on the output above, the dead timer shows that the neighbor relationships have already been established, so the state will be Full for all neighbors, and since the OSPF priorities are all set to 1, the router with the highest router ID will be the DR.
QUESTION 23
The Certkiller backbone OSPF network is shown below:
Refer to the exhibit. All routers have been simultaneously rebooted, and neighbor relationships have been established. Which two statements are true? (Choose two.)
A. The Certkiller 1 RID is 1.1.1.1.
B. The Certkiller 1 RID is 10.1.1.1.
C. The Certkiller 1 RID is 192.168.1.1.
D. The Certkiller 2 RID is 10.1.1.2.
E. The Certkiller 2 RID is 192.168.1.2.
F. The Certkiller 2 RID is 192.168.2.1.
Correct Answer: BD Section: (none) Explanation Explanation/Reference:
Explanation: Remember that the RID is the highest IP address on the box or the loopback interface, calculated at boot time or whenever the OSPF process is restarted. Although the other interfaces on routers Certkiller 1 and Certkiller 2 are higher, the loopback interface is always used as the router ID. If more than one loopback interface is configured, the loopback interface with the highest IP address is chosen as the Router ID.
QUESTION 24
Which type of Link State Announcement will Certkiller E use to announce changes in network 22 to Area 1?
A. Type 1 LSA
B. Type 2 LSA
C. Type 3 LSA
D. Type 4 LSA
E. Type 5 LSA
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Explanation: The external link LSA is originated by AS boundary routers and is flooded throughout the AS. Each external advertisement describes a router to a destination in another autonomous system. Default routes for the AS can also be described by AS external advertisements. This is identified as a Type 5 LSA.
QUESTION 25
What is the OSPF cost for the 100 Mbps Ethernet media type?
A. 1
B. 2
C. 6
D. 10
E. 100
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
By default, OSPF uses the formula of 100,000,000 (100M) divided by bandwidth, or 100,000,000/BW. For
a
100M fast Ethernet connection, the formula is 100M/100M = 1.
QUESTION 26
As a Certkiller .com network technician you are required to drag the appropriate IS-IS routing item to its correct definition.
A.
B.
C.
D.
Correct Answer: Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 27
Given the NSAP 39.0100.0102.0001.0c00.1211.00, which portion is interpreted by IS-IS as the area?
B. 39.0100
C. 39.0100.0102
D. 0001
E. 0001.0c00
F. 0001.0c00.1211
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: A NET is a NSAP where the last byte is always zero. On a router running IS-IS, a NET can be 8 to 20 B in length. The last byte is always the n-selector and must be zero. The n-selector indicates which transport entity the packet is sent to. An n-selector of zero indicates no transport entity, and means that the packet is for the routing software of the system. The six bytes directly preceding the n-selector are the system ID. The system ID length is a fixed size and cannot be changed. The system ID must be unique throughout each area (Level 1) and throughout the backbone (Level 2). All bytes preceding the system ID are the area ID. The area ID field is the portion of the NSAP preceding the system ID. The following example shows a router with area ID 47.0004.004d.0001 and system ID 0001.0c11.1110: 47.0004.004d.0001.0001.0c11.1110.00 In our example, the six bytes preceding the N selector is 0001.0c00.1211 which is the system ID. The portion preceding this, 39.0100.0102, is the area ID.
QUESTION 28
Which two commands can be used to verify that RIPv2 authentication is working properly to ensure that RIP neighbors form adjacencies properly? (Choose two.)
A. show interface
B. show ip route
C. show ip protocols
D. debug ip rip
E. debug ip rip authentication
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Explanation: Verifying Plain Text Authentication RIP version 2 routers can use either plain text or MD5 authentication. By configuring the routers using RIPv2 authentication, all routing update exchanges will be authenticated before being accepted. This can be verified by observing the output obtained from thedebugip rip and show ip route commands. RB#debug ip rip RIP protocol debugging is on *Mar 3
02:11:39.207: RIP: received packet with text authentication 234 *Mar 3 02:11:39.211: RIP: received v2 update from 141.108.0.10 on Serial0 *Mar 3 02:11:39.211: RIP: 70.0.0.0/8 via 0.0.0.0 in 1 hops RB#show ip route R 70.0.0.0/8 [120/1] via 141.108.0.10, 00:00:25, Serial0 80.0.0.0/24 is subnetted, 1 subnets C
80.80.80.0 is directly connected, Loopback0 141.108.0.0/30 is subnetted, 1 subnets C 141.108.0.8 is directly connected, Serial0 Using plain text authentication improves the network design by preventing the addition of routing updates originated by routers not meant to take part in the local routing exchange process. However, this type of authentication is not secure. The password (234 in this example) is exchanged in plain text. It can be captured easily and thus exploited. As mentioned before, MD5 authentication must be preferred over plain text authentication when security is an issue. Verifying MD5 Authentication By configuring the RA and RB routers as shown above, all routing update exchanges will be authenticated before being accepted. This can be verified by observing the output obtained from the debug ip rip and show ip route commands. RB#debug ip rip RIP protocol debugging is on *Mar 3 20:48:37.046: RIP: received packet with MD5 authentication *Mar 3 20:48:37.046: RIP: received v2 update from
141.108.0.10 on Serial0 *Mar 3 20:48:37.050: 70.0.0.0/8 via 0.0.0.0 in 1 hops RB#show ip route R 70.0.0.0/8 [120/1] via 141.108.0.10, 00:00:03, Serial0 80.0.0.0/24 is subnetted, 1 subnets C 80.80.80.0 is directly connected, Loopback0 141.108.0.0/30 is subnetted, 1 subnets C 141.108.0.8 is directly connected, Serial0 MD5 authentication uses the one-way, MD5 hash algorithm, acknowledged to be a strong hashing algorithm. In this mode of authentication, the routing update does not carry the password for the purpose of authentication. Rather, a 128-bit message, generated by running the MD5 algorithm on the password, and the message are sent along for authentication. Thus, it is recommended to use MD5 authentication over plain text authentication since it is more secure. Reference: http://www.cisco.com/en/US/tech/ CK3 65/technologies_configuration_example09186a0080093f1c.shtml#veri
QUESTION 29
1.
all routers are using BGP
2.
synchronization is OFF in AS 647000
A. Router CK6
B. Routers CK2 and CK6
C. Routers CK2 , CK4 , and CK6
D. Routers CK2 , CK3 , CK4 , and CK6
E. Routers CK1 , CK2 , CK3 , CK4 , and CK6
F. Routers CK1 , CK2 , CK3 , CK4 , CK5 , and CK6
G. It will not be propagated to any other router
Correct Answer: FEACDGB Section: (none) Explanation
QUESTION 30
A.
B.
C.
D.
Correct Answer: Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 31
Which attribute must exist in the BGP update packet?
A. LOCAL_PREF
B. AGGREGATOR
C. AS_Path
D. Weight
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
The AS PATH is a well known mandatory attribute. Mandatory means that it is required by all routers.
These
attributes are required and are therefore recognized by all BGP implementations.
QUESTION 32
BGP contains two paths to a destination. Assuming both routes were originated locally and have an equal weight, what will be the next determining factor in choosing the best path?
A. lowest MED
B. highest local preference
C. lowest neighbor IP address
D. lowest origin code
E. shortest AS-path
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation:
How the Best Path Algorithm Works:
BGP assigns the first valid path as the current best path. It then compares the best path with the next path
in list, until it reaches the end of the list of valid paths. The following is a list of rules used to determine the
best path.
1.
Prefer the path with the highest WEIGHT. Note: WEIGHT is a Cisco-specific parameter, local to the router on which it’s configured.
2.
Prefer the path with the highest LOCAL_PREF.
3.
Prefer the path that was locally originated via a network or aggregate BGP subcommand, or through redistribution from an IGP. Local paths sourced by network or redistribute commands are preferred over local aggregates sourced by the aggregate-address command.
4.
Prefer the path with the shortest AS_PATH. Note the following:
5.
Prefer the path with the lowest origin type: IGP is lower than EGP, and EGP is lower than INCOMPLETE.
6.
Prefer the path with the lowest multi-exit discriminator (MED). Note the following:
7.
Prefer external (eBGP) over internal (iBGP) paths. If bestpath is selected, go to Step 9 (multipath).
8.
Prefer the path with the lowest IGP metric to the BGP next hop. Continue, even if bestpath is already selected.
9.
Check if multiple paths need to be installed in the routing table for BGP Multipath. Continue, if bestpath is not selected yet.
10.
When both paths are external, prefer the path that was received first (the oldest one). This step minimizes route-flap, since a newer path will not displace an older one, even if it would be the preferred route based on the next decision criteria (Steps 11, 12, and 13).
11.
Prefer the route coming from the BGP router with the lowest router ID. The router ID is the highest IP address on the router, with preference given to loopback addresses. It can also be set manually using the bgp router-id command.
12.
If the originator or router ID is the same for multiple paths, prefer the path with the minimum cluster list length. This will only be present in BGP route-reflector environments. It allows clients to peer with RRs or clients in other clusters. In this scenario, the client must be aware of the RR-specific BGP attribute.
13.
Prefer the path coming from the lowest neighbor address. This is the IP address used in the BGP neighbor configuration, and corresponds to the remote peer used in the TCP connection with the local router.
QUESTION 33
The Certkiller WAN is displayed below:
You work as an administrator at Certkiller .com. Study the exhibits carefully.
BGP is configured on all routers, synchronization is turned off, and one of the default attributes have
been changed except the MED attribute on Certkiller 5.
Which path is preferred by Certkiller 2 to reach the network 200.200.200.0/24?
A. Certkiller 2- Certkiller 1 because it is the shortest path.
B. Certkiller 2- Certkiller 1 because it has a higher metric.
C. Certkiller 3- Certkiller 4- Certkiller 5 because it has a lower administrative distance.
D. Certkiller 3- Certkiller 4- Certkiller 5 because it has a lower metric.
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:
In BGP, the lowest MED metric is preferred over a higher metric. By default, the value of the metric is 0, so
for AS 200, the path via Certkiller 5 will have a metric of 0, and the path via Certkiller 1 will have a metric of
150, so the path from Certkiller 5 will be preferred.
QUESTION 34
Which BGP path attribute is Cisco proprietary?
A. weight
B. MED
C. local preference
D. origin
E. next-hop
F. AS-path
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation: The WEIGHT attribute is a Cisco proprietary feature used to measure a route’s preference. The WEIGHT inbound route maps. Use the WEIGHT attribute to influence routes from multiple service providers to a central location. Like LOCAL_PREF, assigning a higher weight to a route makes that route more preferred. The WEIGHT attribute also has the highest precedence of any BGP attribute. Reference: CCIE Practical Studies: Configuring Route-Maps and Policy-based Routing, Karl Solie, Cisco Press.
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