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Q1. Refer to the exhibit.
If OSPF is implemented on the network, which additional configuration is needed to allow traffic from host 10.4.1.15/24 to host 10.1.2.20/24?
A. A virtual link between router 2 and router 4
B. A virtual link between router 3 and router 4
C. A virtual link between router 2 and router 3
D. The current design allows traffic between the two hosts.
Answer: D
Explanation:
This specific traffic from 10.4.1.0/24 to 10.1.2.0/24 would work because this traffic crosses only over the single OSPF area of 0.0.0.1.
However, traffic from hosts on R4 to R1 would indeed need a virtual link, since area 0.0.0.2 is not connected to the backbone area of 0.0.0.0.
Q2. Which statement is true regarding the UDP checksum?
A. It is used for congestion control.
B. It cannot be all zeros.
C. It is used by some Internet worms to hide their propagation.
D. It is computed based on the IP pseudo-header.
Answer: D
Explanation:
The method used to compute the checksum is defined in RFC 768: “Checksum is the 16-bit one's complement of the one's complement sum of a pseudo header of information from the IP header, the UDP header, and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.” In other words, all 16-bit words are summed using one's complement arithmetic. Add the 16-bit values up. Each time a carry-out (17th bit) is produced, swing that bit around and add it back into the least significant bit. The sum is then one's complemented to yield the value of the UDP checksum field. If the checksum calculation results in the value zero (all 16 bits 0) it should be sent as the one's complement (all 1s).
Reference: http://en.wikipedia.org/wiki/User_Datagram_Protocol
Q3. Which two statements are true about RSTP? (Choose two.)
A. By default, RTSP uses a separate TCN BPDU when interoperating with 802.1D switches.
B. By default, RTSP does not use a separate TCN BPDU when interoperating with 802.1D switches.
C. If a designated port receives an inferior BPDU, it immediately triggers a reconfiguration.
D. By default, RTSP uses the topology change TC flag.
E. If a port receives a superior BPDU, it immediately replies with its own information, and no reconfiguration is triggered.
Answer: B,D
Explanation:
The RSTP does not have a separate topology change notification (TCN) BPDU. It uses the topology change (TC) flag to show the topology changes.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2950/software/release/12-1_9_ea1/configuration/guide/scg/swmstp.html
Q4. Which cache aggregation scheme is supported by NetFlow ToS-based router aggregation?
A. prefix-port
B. AS
C. protocol port
D. destination prefix
Answer: A
Q5. Which type of EIGRP routes are summarized by the auto-summary command?
A. internal routes that are learned from a peer that is outside the range of local network statements
B. external routes that are learned from a peer that is inside the range of local network statements
C. locally created routes that are outside the range of local network statements
D. external routes that are learned from a peer that is outside the range of local network statements
Answer: B
Explanation:
Auto-Summarization of External Routes
EIGRP will not auto-summarize external routes unless there is a component of the same major network that is an internal route. To illustrate, let us look at Figure 15.
Router Three is injecting external routes to 192.1.2.0/26 and 192.1.2.64/26 into EIGRP using the redistribute connected command, as shown in the configurations below.
Router Three
interface Ethernet0
ip address 192.1.2.1 255.255.255.192
!
interface Ethernet1
ip address 192.1.2.65 255.255.255.192
!
interface Ethernet2
ip address 10.1.2.1 255.255.255.0
!router eigrp 2000
redistribute connected
network 10.0.0.0
default-metric 10000 1 255 1 1500
With this configuration on Router Three, the routing table on Router One shows:
one# show ip route
10.0.0.0/8 is subnetted, 2 subnets
D 10.1.2.0 [90/11023872] via 10.1.50.2, 00:02:03, Serial0
C 10.1.50.0 is directly connected, Serial0
192.1.2.0/26 is subnetted, 1 subnets
D EX 192.1.2.0 [170/11049472] via 10.1.50.2, 00:00:53, Serial0
D EX 192.1.2.64 [170/11049472] via 10.1.50.2, 00:00:53, Serial0
Although auto-summary normally causes Router Three to summarize the 192.1.2.0/26 and 192.1.2.64/26 routes into one major net destination (192.1.2.0/24), it does not do this because both routes are external. However, if you reconfigure the link between Routers Two and Three to 192.1.2.128/26, and add network statements for this network on Routers Two and Three, the 192.1.2.0/24 auto-summary is then generated on Router Two.
Router Three
interface Ethernet0
ip address 192.1.2.1 255.255.255.192
!
interface Ethernet1
ip address 192.1.2.65 255.255.255.192
!
interface Serial0
ip address 192.1.2.130 255.255.255.192
!
router eigrp 2000 network 192.1.2.0
Now Router Two generates the summary for 192.1.2.0/24:
two# show ip route
D 192.1.2.0/24 is a summary, 00:06:48, Null0
And Router One shows only the summary routE.
one# show ip route
10.0.0.0/8 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0
D 192.1.2.0/24 [90/11023872] via 10.1.50.2, 00:00:36, Serial0
Reference: http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/16406-eigrp-toc.html
Q6. Which two statements about the C-bit and PW type are true? (Choose two.)
A. The C-bit is 1 byte and the PW type is 15 bytes.
B. The PW type indicates the type of pseudowire.
C. The C-bit is 3 bits and the PW type is 10 bits.
D. The C-bit set to 1 indicates a control word is present.
E. The PW type indicates the encryption type.
Answer: B,D
Explanation:
The control word carries generic and Layer 2 payload-specific information. If the C-bit is set to 1, the advertising PE expects the control word to be present in every pseudowire packet on the pseudowire that is being signaled. If the C-bit is set to 0, no control word is expected to be present. Pseudowire Type—PW Type is a 15-bit field that represents the type of pseudowire.
Reference: http://www.ciscopress.com/articles/article.asp?p=386788&seqNum=2
Q7. Refer to the exhibit.
Video Source S is sending interactive video traffic to Video Receiver R. Router R1 has multiple routing table entries for destination R. Which load-balancing mechanism on R1 can cause out-of-order video traffic to be received by destination R?
A. per-flow load balancing on R1 for destination R
B. per-source-destination pair load balancing on R1 for destination R
C. CEF load balancing on R1 for destination R
D. per-packet load balancing on R1 for destination R
Answer: D
Explanation:
Per-packet load balancing guarantees equal load across all links, however potentially the packets may arrive out-of-order at the destination as differential delay may exist within the network.
Reference: http://www.cisco.com/en/US/products/hw/modules/ps2033/prod_technical_reference09186 a00800afeb7.html
Q8. Which authentication method does OSPFv3 use to secure communication between neighbors?
A. plaintext
B. MD5 HMAC
C. PKI
D. IPSec
Answer: D
Explanation:
In order to ensure that OSPFv3 packets are not altered and re-sent to the device, causing the device to behave in a way not desired by its system administrators, OSPFv3 packets must be authenticated. OSPFv3 uses the IPsec secure socket API to add authentication to OSPFv3 packets. This API supports IPv6. OSPFv3 requires the use of IPsec to enable authentication. Crypto images are required to use authentication, because only crypto images include the IPsec API needed for use with OSPFv3.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-sy/iro-15-sy-book/ip6-route-ospfv3-auth-ipsec.html
Q9. Refer to the exhibit.
What is a reason for the RIB-failure?
A. CEF is not enabled on this router.
B. The route 10.100.1.1/32 is in the routing table, but not as a BGP route.
C. The routing table has yet to be updated with the BGP route.
D. The BGP route is filtered inbound and hence is not installed in the routing table.
Answer: B
Explanation:
A rib-failure occurs when BGP tries to install the bestpath prefix into the RIB, but the RIB rejects the BGP route because a route with better administrative distance already exists in the routing table. An inactive Border Gateway Protocol (BGP) route is a route that is not installed in the RIB, but is installed in the BGP table as rib-failure. Example Topology Router 1 (R1) and router 2 (R2) have two parallel links; one links runs BGP AS 65535 and the other link runs Enhanced Interior Gateway Routing Protocol (EIGRP) AS 1. Both BGP and EIGRP are advertising the network 10.1.1.1/32 on R1.
R2 learns about the 1.1.1.1/32 route through both EIGRP and BGP, but installs only the EIGRP route in the routing table because of the lower administrative distance. Since the BGP route is not installed in the R2 routing table, the route appears as a rib-failure in the R2 BGP table.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/116146-config-bgp-next-hop-00.html
Q10. Which two statements about IBGP multipath are true? (Choose two.)
A. The IGP metric of the BGP next hop can be different from the best-path IGP metric if you configure the router for unequal-cost IBGP multipath.
B. The IGP metric of the BGP next hop must be the same as the best-path IGP metric.
C. The equivalent next-hop-self is performed on the best path from among the IBGP multipaths before it is forwarded to external peers.
D. The path should be learned from an external neighbor.
E. The router BGP process must learn the path from a confederation-external or external neighbor.
F. The router BGP process must learn the path from an internal neighbor.
Answer: A,F