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Q1. Refer to the exhibit.
All switches have default bridge priorities, and originate BPDUs with MAC addresses as indicated. The numbers shown are STP link metrics.
After STP converges, you discover that traffic from switch SWG toward switch SWD takes a less optimal path. What can you do to optimize the STP tree in this switched network?
A. Change the priority of switch SWA to a lower value than the default value.
B. Change the priority of switch SWB to a higher value than the default value.
C. Change the priority of switch SWG to a higher value than the default value.
D. Change the priority of switch SWD to a lower value than the default value.
Answer: D
Explanation:
In this topology, we see that all port paths and priorities are the same, so the lowest MAC address will be used to determine the best STP path. From SWG, SWE will be chosen as the next switch in the path because it has a lower MAC address than SWF. From SWE, traffic will go to SWC because it has a lower MAC address, and then to SWD, instead of going from SWE directly to SWD. If we lower the priority of SWD (lower means better with STP) then traffic will be sent directly to SWD.
Q2. In an STP domain, which two statements are true for a nonroot switch, when it receives a configuration BPDU from the root bridge with the TC bit set? (Choose two.)
A. It sets the MAC table aging time to max_age + forward_delay time.
B. It sets the MAC table aging time to forward_delay time.
C. It recalculates the STP topology upon receiving topology change notification from the root switch.
D. It receives the topology change BPDU on both forwarding and blocking ports.
Answer: B,D
Explanation:
When the TC bit is received, every bridge is then notified and reduces the aging time to forward_delay (15 seconds by default) for a certain period of time (max_age + forward_delay). It is more beneficial to reduce the aging time instead of clearing the table because currently active hosts, that effectively transmit traffic, are not cleared from the table. Once the root is aware that there has been a topology change event in the network, it starts to send out its configuration BPDUs with the topology change (TC) bit set. These BPDUs are relayed by every bridge in the network with this bit set. As a result all bridges become aware of the topology change situation and it can reduce its aging time to forward_delay. Bridges receive topology change BPDUs on both forwarding and blocking ports. An important point to consider here is that a TCN does not start a STP recalculation. This fear comes from the fact that TCNs are often associated with unstable STP environments; TCNs are a consequence of this, not a cause. The TCN only has an impact on the aging time. It does not change the topology nor create a loop.
Reference: http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/12013-17.html#topic1
Q3. Refer to the exhibit.
Which statement is true?
A. IS-IS has been enabled on R4 for IPv6, single-topology.
B. IS-IS has been enabled on R4 for IPv6, multitopology.
C. IS-IS has been enabled on R4 for IPv6, single-topology and multitopology.
D. R4 advertises IPv6 prefixes, but it does not forward IPv6 traffic, because the protocol has not been enabled under router IS-IS.
Answer: A
Explanation:
When working with IPv6 prefixes in IS-IS, you can configure IS-IS to be in a single topology for both IPv4 and IPv6 or to run different topologies for IPv4 and IPv6. By default, IS-IS works in single-topology mode when activating IPv4 and IPv6. This means that the IS-IS topology will be built based on IS Reachability TLVs. When the base topology is built, then IPv4 prefixes (IP Reachability TLV) and IPv6 prefixes (IPv6 Reachability TLV) are added to each node as leaves, without checking if there is IPv6 connectivity between nodes.
Reference: https://blog.initialdraft.com/archives/3381/
Q4. Which circumstance can cause TCP starvation and UDP dominance to occur?
A. Too few queues are available.
B. UDP is comprised of smaller packets than TCP.
C. Retransmitted TCP packets are on the network.
D. UDP and TCP data are assigned to the same service-provider class.
Answer: D
Q5. Which option is the result if two adjacent routers are configured for OSPF with different process IDs?
A. The routers are unable to establish an adjacency.
B. The routers establish an adjacency, but route exchange fails.
C. The routers establish an adjacency and exchange routes, but the routes are unreachable.
D. The routers establish an adjacency and exchange routes, and the routes are reachable.
Answer: D
Q6. Which two metrics are measured with active probes when PfR voice traffic optimization is in use? (Choose two.)
A. MOS
B. cost
C. jitter
D. bandwidth
Answer: A,C
Q7. Refer to the exhibit.
Why is the neighbor relationship between R2 and R4 shown as ES-IS?
A. because there is an MTU mismatch between R2 and R4
B. because interface S3/0 of R4 is configured as L1/L2
C. because interface S3/0 of R2 is configured as L1
D. because there is a hello interval mismatch between R2 and R4
Answer: C
Explanation:
With IS-IS we will see ES-IS when one of the following is true:
. uk.co.certification.simulator.questionpool.PList@138b7160
So in this question because we do not know about the other side’s “show CLNS neighbor” A must be the better choose.
Q8. In which type of EIGRP configuration is EIGRP IPv6 VRF-Lite available?
A. stub
B. named mode
C. classic mode
D. passive
Answer: B
Explanation:
The EIGRP IPv6 VRF Lite feature provides EIGRP IPv6 support for multiple VRFs. EIGRP for IPv6 can operate in the context of a VRF. The EIGRP IPv6 VRF Lite feature provides
separation between routing and forwarding, providing an additional level of security because no communication between devices belonging to different VRFs is allowed unless it is explicitly configured. The EIGRP IPv6 VRF Lite feature simplifies the management and troubleshooting of traffic belonging to a specific VRF. The EIGRP IPv6 VRF Lite feature is available only in EIGRP named configurations.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/configuration/15-2mt/ipv6-15-2mt-book/ip6-eigrp.html#GUID-92B4FF4F-2B68-41B0-93C8-AAA4F0EC1B1B
Q9. Refer to the exhibit.
Which two statements are true? (Choose two.)
A. This router is not 4-byte autonomous system aware.
B. This router is 4-byte autonomous system aware.
C. The prefix 10.100.1.1/32 was learned through an autonomous system number with a length of 4 bytes, and this router is 4-byte autonomous system aware.
D. The prefix 10.100.1.1/32 was learned through an autonomous system number with a length of 4 bytes, and this router is not 4-byte autonomous system aware.
E. The prefix 10.100.1.1/32 was originated from a 4-byte autonomous system.
Answer: A,D
Explanation:
Prior to January 2009, BGP autonomous system (AS) numbers that were allocated to companies were 2-octet numbers in the range from 1 to 65535 as described in RFC 4271, A Border Gateway Protocol 4 (BGP-4). Due to increased demand for AS numbers, the Internet Assigned Number Authority (IANA) started to allocate four-octet AS numbers in the range from 65536 to 4294967295. RFC 5396, Textual Representation of Autonomous System (AS) Numbers, documents three methods of representing AS numbers. Cisco has implemented the following two methods:
. Asplain — Decimal value notation where both 2-byte and 4-byte AS numbers are represented by their decimal value. For example, 65526 is a 2-byte AS number and 234567 is a 4-byte AS number.
. Asdot — Autonomous system dot notation where 2-byte AS numbers are represented by their decimal value and 4-byte AS numbers are represented by a dot notation. For example, 65526 is a 2-byte AS number and 1.169031 is a 4-byte AS number (this is dot notation for the 234567 decimal number).
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-4byte-asn.html
Q10. Refer to the exhibit.
While troubleshooting high CPU utilization on one of your Cisco Catalyst switches, you find that the issue is due to excessive flooding that is caused by STP. What can you do to prevent this issue from happening again?
A. Disable STP completely on the switch.
B. Change the STP version to RSTP.
C. Configure PortFast on port-channel 1.
D. Configure UplinkFast on the switch.
E. Configure PortFast on interface Gi0/15.
Answer: E
Explanation:
Topology Changes (TC) should be a rare event in a well-configured network. When a link on a switch port goes up or down, there is eventually a TC, once the STP state of the port is changing to or from forwarding. When the port is flapping, this would cause repetitive TCs and flooding.
Ports with the STP portfast feature enabled will not cause TCs when going to or from the forwarding state. The configuration of portfast on all end-device ports (such as printers, PCs, and servers) should limit TCs to a low amount and is highly recommended.
Reference: http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/28943-170.html
Q11. Which two statements about BPDU guard are true? (Choose two.)
A. The global configuration command spanning-tree portfast bpduguard default shuts down interfaces that are in the PortFast-operational state when a BPDU is received on that port.
B. The interface configuration command spanning-tree portfast bpduguard enable shuts down only interfaces with PortFast enabled when a BPDU is received.
C. BPDU guard can be used to prevent an access port from participating in the spanning tree in the service provider environment.
D. BPDU guard can be used to protect the root port.
E. BPDU guard can be used to prevent an invalid BPDU from propagating throughout the network.
Answer: A,C
Q12. Which three options are best practices for implementing a DMVPN? (Choose three.)
A. Use IPsec in tunnel mode.
B. Implement Dead Peer Detection to detect communication loss.
C. Configure AES for encryption of transported data.
D. Configure SHA-1 for encryption of transported data.
E. Deploy IPsec hardware acceleration to minimize router memory overhead.
F. Configure QoS services only on the head-end router.
Answer: A,B,C
Explanation:
Best Practices Summary for Hub-and-Spoke Deployment Model
This section describes the best practices for a dual DMVPN cloud topology with the hub-and-spoke deployment, supporting IP multicast (IPmc) traffic including routing protocols.
The following are general best practices:
. Use IPsec in transport mode
. Configure Triple DES (3DES) or AES for encryption of transported data (exports of encryption algorithms to certain countries may be prohibited by law).
Implement Dead Peer Detection (DPD) on the spokes to detect loss of communication between peers.
. Deploy hardware-acceleration of IPsec to minimize router CPU overhead, to support traffic with low latency and jitter requirements, and for the highest performance for cost.
. Keep IPsec packet fragmentation to a minimum on the customer network by setting MTU size or using Path MTU Discovery (PMTUD).
. Use Digital Certificates/Public Key Infrastructure (PKI) for scalable tunnel authentication.
. Configure a routing protocol (for example, EIGRP, BGP or OSPF) with route summarization help alleviate interface congestion issues and to attempt to keep higher priority traffic from being dropped during times of congestion.
Reference: http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/DMVPDG/DMV PN_1.html
Q13. Which two statements about OSPFv3 are true? (Choose two.)
A. It supports unicast address families for IPv4 and IPv6.
B. It supports unicast address families for IPv6 only.
C. It supports only one address family per instance.
D. It supports the use of a cluster ID for loop prevention.
E. It supports multicast address families for IPv4 and IPv6.
F. It supports multicast address families for IPv6 only.
Answer: A,C
Q14. Refer to the exhibit.
The two standalone chassis are unable to convert into a VSS. What can you do to correct the problem?
A. Set a different port channel number on each chassis.
B. Set a different virtual domain ID on each chassis.
C. Set the redundancy mode to rpr on both chassis.
D. Add two ports to the port channel group.
Answer: A
Q15. Refer to the exhibit.
Which two statements about the EEM applet configuration are true? (Choose two.)
A. The EEM applet runs before the CLI command is executed.
B. The EEM applet runs after the CLI command is executed.
C. The EEM applet requires a case-insensitive response.
D. The running configuration is displayed only if the letter Y is entered at the CLI.
Answer: A,D
Explanation:
sync Indicates whether the policy should be executed synchronously before the CLI command executes.
. If the yes keyword is specified, the policy will run synchronously with the CLI command.
. If the no keyword is specified, the policy will run asynchronously with the CLI command.
nocase
(Optional) Specifies case insensitive comparison.
Here we see that the sync knob was enabled so A is correct. However, C is not correct as the nocase argument was not used, so the applet is configured to display the config only if a capital Y is issued.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/eem/command/eem-cr-book/eem-cr-a2.html