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Q61. Which two statements are true about an EPL? (Choose two.)
A. It is a point-to-point Ethernet connection between a pair of NNIs.
B. It allows for service multiplexing.
C. It has a high degree of transparency.
D. The EPL service is also referred to as E-line.
Answer: C,D
Explanation:
Ethernet private line (EPL) and Ethernet virtual private line (EVPL) are carrier Ethernet data services defined by the Metro Ethernet Forum. EPL provides a point-to-point Ethernet virtual connection (EVC) between a pair of dedicated user–network interfaces (UNIs), with a high degree of transparency. EVPL provides a point-to-point or point-to-multipoint connection between a pair of UNIs. The services are categorized as an E-Line service type, with an expectation of low frame delay, frame delay variation and frame loss ratio. EPL is implemented using a point-to-point (EVC) with no Service Multiplexing at each UNI (physical interface), i.e., all service frames at the UNI are mapped to a single EVC (a.k.a. all-to-one bundling).
Reference: http://en.wikipedia.org/wiki/Ethernet_Private_Line
Q62. Which two options are ways in which an OSPFv3 router handles hello packets with a clear address-family bit? (Choose two.)
A. IPv4 unicast packets are discarded.
B. IPv6 unicast packets are discarded.
C. IPv4 unicast packets are forwarded.
D. IPv6 unicast packets are forwarded.
Answer: A,D
Explanation:
A typical distance vector protocol saves the following information when computing the best path to a destination: the distance (total metric or distance, such as hop count) and the vector (the next hop). For instance, all the routers in the network in Figure 1 are running Routing Information Protocol (RIP). Router Two chooses the path to Network A by examining the hop count through each available path.
Since the path through Router Three is three hops, and the path through Router One is two hops, Router Two chooses the path through One and discards the information it learned through Three. If the path between Router One and Network A goes down, Router Two loses all connectivity with this destination until it times out the route of its routing table (three update periods, or 90 seconds), and Router Three re-advertises the route (which occurs every 30 seconds in RIP). Not including any hold-down time, it will take between 90 and 120 seconds for Router Two to switch the path from Router One to Router Three. EIGRP, instead of counting on full periodic updates to re-converge, builds a topology table from each of its neighbor's advertisements (rather than discarding the data), and converges by either looking for a likely loop-free route in the topology table, or, if it knows of no other route, by querying its neighbors. Router Two saves the information it received from both Routers One and Three. It chooses the path through One as its best path (the successor) and the path through Three as a loop-free path (a feasible successor). When the path through Router One becomes unavailable, Router Two examines its topology table and, finding a feasible successor, begins using the path through Three immediately.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/16406-eigrp-toc.html
Q63. What is the function of the command ip pim autorp listener?
A. It allows a border PIM sparse mode router to accept autorp information from another autonomous system.
B. It allows the mapping agents to accept autorp information from the PIM rendezvous point.
C. It allows the routers to flood the autorp information in a sparse-mode-only network.
D. It allows a BSR to accept autorp information and translate it into BSR messages.
Answer: C
Explanation:
To cause IP multicast traffic for the two Auto-RP groups 224.0.1.39 and 224.0.1.40 to be Protocol Independent Multicast (PIM) dense mode flooded across interfaces operating in PIM sparse mode, use the ip pim autorp listener command in global configuration mode. To disable this feature, use the no form of this command.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr-book/imc_i3.html#wp3085748429
Q64. Refer to the exhibit.
Which statement about this IP SLA is true?
A. The SLA must also have a schedule configured before it will start.
B. The TTL of the SLA packets is 10.
C. The SLA has a timeout of 3.6 seconds.
D. The SLA has a lifetime of 5 seconds.
Answer: A
Explanation:
When you configure an IP SLAs operation, you must schedule the operation to begin capturing statistics and collecting error information. You can schedule an operation to start immediately or to start at a certain month, day, and hour. You can use the pending option to set the operation to start at a later time. The pending option is an internal state of the operation that is visible through SNMP. The pending state is also used when an operation is a reaction (threshold) operation waiting to be triggered. You can schedule a single IP SLAs operation or a group of operations at one time. We can see in this output that the IP SLA is still in a pending trigger state.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/44sg/configuration/guide/Wrapper-44SG/swipsla.html
Q65. Refer to the exhibit.
Which two possible network conditions can you infer from this configuration? (Choose two.)
A. The authentication parameters on R1 and R2 are mismatched.
B. R1 is using the default NTP source configuration.
C. R1 and R2 have established an NTP session.
D. R2 is configured as the NTP master with a stratum of 7.
Answer: A,B
Explanation:
Answer A. The NTP associations are not synced, it is only listed as a candidate because it was configured. Routing is not the issue, so it must be mismatched authentication parameters.
Answer B. NTP sets the source IP address for all NTP packets based on the address of the interface through which the NTP packets are sent. You can configure NTP to use a specific source IP address.
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Q66. Which two options are EIGRP route authentication encryption modes? (Choose two.)
A. MD5
B. HMAC-SHA-256bit
C. ESP-AES
D. HMAC-AES
Answer: A,B
Explanation:
Packets exchanged between neighbors must be authenticated to ensure that a device accepts packets only from devices that have the same preshared authentication key. Enhanced Interior Gateway Routing Protocol (EIGRP) authentication is configurable on a per-interface basis; this means that packets exchanged between neighbors connected through an interface are authenticated. EIGRP supports message digest algorithm 5 (MD5) authentication to prevent the introduction of unauthorized information from unapproved sources. MD5 authentication is defined in RFC 1321. EIGRP also supports the Hashed Message Authentication Code-Secure Hash Algorithm-256 (HMAC-SHA-256) authentication method.
Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe-3s/ire-xe-3s-book/ire-sha-256.html
Q67. Consider an OSPFv3 network with four parallel links between each pair of routers. Which measure can you use to reduce the CPU load and at the same time keep all links available for ECMP?
A. Configure some interfaces as passive interface.
B. Configure ipv6 ospf priority 0 on some interfaces.
C. Configure some routers with a distribute list in ingress of the OSPFv3 process.
D. Configure ipv6 ospf database-filter all out on some interfaces.
Answer: D
Explanation:
To filter outgoing link-state advertisements (LSAs) to an Open Shortest Path First version 3 (OSPFv3) interface, use the ipv6 ospf database-filter all out command in interface configuration mode. This can be done on some of the links to reduce the CPU load while still ensuring that all links in the equal cost path are still being used.
Q68. What is a cause for unicast flooding?
A. Unicast flooding occurs when multicast traffic arrives on a Layer 2 switch that has directly connected multicast receivers.
B. When PIM snooping is not enabled, unicast flooding occurs on the switch that interconnects the PIM-enabled routers.
C. A man-in-the-middle attack can cause the ARP cache of an end host to have the wrong MAC address. Instead of having the MAC address of the default gateway, it has a MAC address of the man-in-the-middle. This causes all traffic to be unicast flooded through the man-in-the-middle, which can then sniff all packets.
D. Forwarding table overflow prevents new MAC addresses from being learned, and packets destined to those MAC addresses are flooded until space becomes available in the forwarding table.
Answer: D
Explanation:
Causes of Flooding The very cause of flooding is that destination MAC address of the packet is not in the L2 forwarding table of the switch. In this case the packet will be flooded out of all forwarding ports in its VLAN (except the port it was received on). Below case studies display most common reasons for destination MAC address not being known to the switch.
Cause 1: Asymmetric Routing
Large amounts of flooded traffic might saturate low-bandwidth links causing network performance issues or complete connectivity outage to devices connected across such low-bandwidth links
Cause 2: Spanning-Tree Protocol Topology Changes
Another common issue caused by flooding is Spanning-Tree Protocol (STP) Topology Change Notification (TCN). TCN is designed to correct forwarding tables after the forwarding topology has changed. This is necessary to avoid a connectivity outage, as after a topology change some destinations previously accessible via particular ports might become accessible via different ports. TCN operates by shortening the forwarding table aging time, such that if the address is not relearned, it will age out and flooding will occur
Cause 3: Forwarding Table Overflow
Another possible cause of flooding can be overflow of the switch forwarding table. In this case, new addresses cannot be learned and packets destined to such addresses are flooded until some space becomes available in the forwarding table. New addresses will then be learned. This is possible but rare, since most modern switches have large enough forwarding tables to accommodate MAC addresses for most designs.
Reference:
http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6000-series-switches/23563-143.html
Q69. Two routers are trying to establish an OSPFv3 adjacency over an Ethernet link, but the adjacency is not forming. Which two options are possible reasons that prevent OSPFv3 to form between these two routers? (Choose two.)
A. mismatch of subnet masks
B. mismatch of network types
C. mismatch of authentication types
D. mismatch of instance IDs
E. mismatch of area types
Answer: D,E
Explanation:
An OSPFv3 interface must have a compatible configuration with a remote interface before the two can be considered neighbors. The two OSPFv3 interfaces must match the following criteria:
. Hello interval
. Dead interval
. Area ID
. Optional capabilities
The OSPFv3 header includes an instance ID field to identify that OSPFv3 packet for a particular OSPFv3 instance. You can assign the OSPFv3 instance. The interface drops all OSPFv3 packets that do not have a matching OSPFv3 instance ID in the packet header.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/unicast/configuration/guide/l3_cli_nxos/l3_ospfv3.html
Q70. Refer to the exhibit.
R3 is failing to join the multicast group 224.1.1.1 that is sourcing from R1. Which two actions can you take to allow multicast traffic to flow correctly? (Choose two.)
A. Remove the static multicast route on R1.
B. Configure OSPF on R1 and R3 to include the tunnel interfaces.
C. Add an additional static multicast route on R2 for multicast group 224.1.1.1 toward R3.
D. Replace the static multicast route on R1 to send traffic toward R2.
E. Remove the static unicast route on R1.
F. Add an additional static unicast route on R2 toward the loopback interface of R3.
Answer: A,B
Explanation:
Since the tunnel interfaces are not part of OSPF, the best path to the multicast source of R1 from R3 would be over the Gi0/0 path via OSPF. However, the static mroute is configured to use the tunnel, so this causes an RPF failure used in Sparse Mode. Best fix is to add the tunnel interfaces into OSPF and remove the static mroute so that that the RPF check no longer fails.