Answer: A,B 

Answer:  

Answer: A,B 

Explanation: 

The BGP Support for Next-Hop Address Tracking feature is enabled by default when a supporting Cisco software image is installed. BGP next-hop address tracking is event driven. BGP prefixes are automatically tracked as peering sessions are established. Next-hop changes are rapidly reported to the BGP routing process as they are updated in the RIB. This optimization improves overall BGP convergence by reducing the response time to next-hop changes for routes installed in the RIB. When a best path calculation is run in between BGP scanner cycles, only next-hop changes are tracked and processed. BGP routers and route reflectors (RRs) propagate only their best path over their sessions. The advertisement of a prefix replaces the previous announcement of that prefix (this behavior is known as an implicit withdraw). The implicit withdraw can achieve better scaling, but at the cost of path diversity. Path hiding can prevent efficient use of BGP multipath, prevent hitless planned maintenance, and can lead to MED oscillations and suboptimal hot-potato routing. Upon nexthop failures, path hiding also inhibits fast and local recovery because the network has to wait for BGP control plane convergence to restore traffic. The BGP Additional Paths feature provides a generic way of offering path diversity; the Best External or Best Internal features offer path diversity only in limited scenarios. The BGP Additional Paths feature provides a way for multiple paths for the same prefix to be advertised without the new paths implicitly replacing the previous paths. Thus, path diversity is achieved instead of path hiding. 

References: http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_bgp/configuration/15-1sg/irg-nexthop-track.html http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/bgp_additional_paths.html 

Answer: D 

Explanation: 

To make sure that your connection is operating properly, IEEE 802.3 Ethernet employs normal link pulses (NLPs), which are used for verifying link integrity in a 10BaseT system. This signaling gives you the link indication when you attach to the hub and is performed between two directly connected link interfaces (hub-to-station or station-to-station). NLPs are helpful in determining that a link has been established between devices, but they are not a good indicator that your cabling is free of problems. An extension of NLPs is fast link pulses. These do not perform link tests, but instead are employed in the autonegotiation process to advertise a device's capabilities. 

Reference: 

http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html 

Answer: C 

Explanation: 

The advertised metric from an EIGRP neighbor (peer) to the local router is called Advertised Distance (or reported distance) while the metric from the local router to that network is called Feasible Distance. For example, R1 advertises network 10.10.10.0/24 with a metric of 20 to R2. For R2, this is the advertised distance. R2 calculates the feasible distance by adding the metric from the advertised router (R1) to itself. So in this case the feasible distance to network 10.10.10.0/24 is 20 + 50 = 70. 

Before a router can be considered a feasible successor, it must pass the feasibility condition rule. In short, the feasibility condition says that if we learn about a prefix from a neighbor, the advertised distance from that neighbor to the destination must be lower than our feasible distance to that same destination. Therefore we see the Advertised Distance always smaller than the Feasible Distance to satisfy the feasibility condition. 

Answer: D 

Explanation: 

NTP uses a concept called “stratum” that defines how many NTP hops away a device is from an authoritative time source. For example, a device with stratum 1 is a very accurate device and might have an atomic clock attached to it. Another NTP server that is using this stratum 1 server to sync its own time would be a stratum 2 device because it’s one NTP hop further away from the source. When you configure multiple NTP servers, the client will prefer the NTP server with the lowest stratum value. 

Reference: https://networklessons.com/network-services/cisco-network-time-protocol-ntp/ 

Answer: B,D,E 

Explanation: 

Here is a list of the differences between OSPFv2 and OSPFv3: 

They use different address families (OSPFv2 is for IPv4-only, OSPFv3 can be used for IPv6-only or both protocols (more on this following)) 

OSPFv3 introduces new LSA types 

OSPFv3 has different packet format 

OSPFv3 uses different flooding scope bits (U/S2/S1) 

OSPFv3 adjacencies are formed over link-local IPv6 communications 

OSPFv3 runs per-link rather than per-subnet 

OSPFv3 supports multiple instances on a single link, Interfaces can have multiple IPv6 addresses 

OSPFv3 uses multicast addresses FF02::5 (all OSPF routers), FF02::6 (all OSPF DRs) 

OSPFv3 Neighbor Authentication done with IPsec (AH) 

OSPFv2 Router ID (RID) must be manually configured, still a 32-bit number 

Following is a simple example of OSPFv3 configuration on a Cisco IOS 12.4T router. 

ipv6 unicast-routing 

ipv6 cef 

! 

interface GigabitEthernet 0/0 

description Area 0.0.0.0 backbone interface 

ipv6 address 2001:DB8:100:1::1/64 

ipv6 ospf network broadcast 

ipv6 ospf 100 area 0.0.0.0 

Reference: http://www.networkworld.com/article/2225270/cisco-subnet/ospfv3-for-ipv4-and-ipv6.html 

Answer: A,B,C 

Explanation: 

Key server is responsible for maintaining security policies, authenticating the Group Members and providing the session key for encrypting traffic. KS authenticates the individual GMs at the time of registration. Only after successful registration the GMs can participate in group SA. 

Reference: http://www.cisco.com/c/en/us/products/collateral/security/group-encrypted-transport-vpn/deployment_guide_c07_554713.html 

Answer: C,D,E 

Explanation: 

Modes are: 

Mode monitor passive 

Passive monitoring is the act of PfR gathering information on user packets assembled into flows by Netflow. Passive monitoring is typically only recommended in Internet edge deployments because active probing is ineffective because of security policies that block probing. PfR, when enabled, automatically enables Netflow on the managed interfaces on the Border Routers. By aggregating this information on the Border Routers and periodically reporting the collected data to the Master Controller, the network prefixes and applications in use can automatically be learned. 

Mode monitor active 

Active monitoring is the act of generating Cisco IOS IP Service Level Agreements (SLAs) probes to generate test traffic for the purpose of obtaining information regarding the characteristics of the WAN links. PfR can either implicitly generates active probes when passive monitoring has identified destination hosts, or the network manager can explicitly configured probes in the PfR configuration. When jitter probes are used (common use case), Target Discovery is used to learn the respond address and to automatically generate the probes. 

Mode monitor Fast 

This mode generates active probes through all exists continuously at the configured probe frequency. This differs from either active or both modes in that these modes only generate probes through alternate paths (exits) in the event the current path is out-of-policy. 

Reference: http://docwiki.cisco.com/wiki/PfR:Technology_Overview#Mode_monitor_passive 

Answer: D