Key benefits of ccie 400 101

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Ucertify offers free demo for 400 101 dumps exam. “CCIE Routing and Switching (v5.0)”, also known as ccie 400 101 dumps exam, is a Cisco Certification. This set of posts, Passing the Cisco 400 101 pdf exam, will help you answer those questions. The ccie 400 101 Questions & Answers covers all the knowledge points of the real exam. 100% real Cisco cisco 400 101 exams and revised by experts!

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Q251. Which statement describes the BGP add-path feature? 

A. It allows for installing multiple IBGP and EBGP routes in the routing table. 

B. It allows a network engineer to override the selected BGP path with an additional path created in the config. 

C. It allows BGP to provide backup paths to the routing table for quicker convergence. 

D. It allows multiple paths for the same prefix to be advertised. 

Answer:

Explanation: 

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. 

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-additional-paths.html 

Q252. Which two statements are true about IS-IS? (Choose two.) 

A. IS-IS DIS election is nondeterministic. 

B. IS-IS SPF calculation is performed in three phases. 

C. IS-IS works over the data link layer, which does not provide for fragmentation and reassembly. 

D. IS-IS can never be routed beyond the immediate next hop. 

Answer: C,D 

Explanation: 

IS-IS runs directly over the data link alongside IP. On Ethernet, IS-IS packets are always 802.3 frames, with LSAPs 0xFEFE while IP packets are either Ethernet II frames or SNAP frames identified with the protocol number 0x800. OSPF runs over IP as protocol number 89. 

IS-IS runs directly over layer 2 and hence: 

-cannot support virtual links unless some explicit tunneling is implemented 

-packets are kept small so that they don't require hop-by-hop fragmentation 

-uses ATM/SNAP encapsulation on ATM but there are hacks to make it use VcMux encapsulation 

-some operating systems that support IP networking have been implemented to differentiate Layer 3 packets in kernel. Such Oss require a lot of kernel modifications to support IS-IS for IP routing. 

-can never be routed beyond the immediate next hop and hence shielded from IP spoofing and similar Denial of Service attacks. 

Reference: https://tools.ietf.org/html/draft-bhatia-manral-diff-isis-ospf-00 

Q253. Refer to the exhibit. 

Which statement describes the effect on the network if FastEthernet0/1 goes down temporarily? 

A. FastEthernet0/2 forwards traffic only until FastEthernet0/1 comes back up. 

B. FastEthernet0/2 stops forwarding traffic until FastEthernet0/1 comes back up. 

C. FastEthernet0/2 forwards traffic indefinitely. 

D. FastEthernet0/1 goes into standby. 

Answer:

Explanation: 

Use the switchport backup interface interface configuration command on a Layer 2 interface to configure Flex Links, a pair of interfaces that provide backup to each other. Use the no form of this command to remove the Flex Links configuration. With Flex Links configured, one link acts as the primary interface and forwards traffic, while the other interface is in standby mode, ready to begin forwarding traffic if the primary link shuts down. The interface being configured is referred to as the active link; the specified interface is identified as the backup link. The feature provides an alternative to the Spanning Tree Protocol (STP), allowing users to turn off STP and still retain basic link redundancy. 

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_53_se/command/reference/2960ComRef/cli3.html#wp3269214 

Q254. Which statement is true about trunking? 

A. Cisco switches that run PVST+ do not transmit BPDUs on nonnative VLANs when using a dot1q trunk. 

B. When removing VLAN 1 from a trunk, management traffic such as CDP is no longer passed in that VLAN. 

C. DTP only supports autonegotiation on 802.1q and does not support autonegotiation for ISL. 

D. DTP is a point-to-point protocol. 

Answer:

Explanation: 

Ethernet trunk interfaces support different trunking modes. You can set an interface as trunking or nontrunking or to negotiate trunking with the neighboring interface. To autonegotiate trunking, the interfaces must be in the same VTP domain. Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Point-to-Point Protocol. However, some internetworking devices might forward DTP frames improperly, which could cause misconfigurations. 

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swvlan.html 

Q255. Which two options are causes of out-of-order packets? (Choose two.) 

A. a routing loop 

B. a router in the packet flow path that is intermittently dropping packets 

C. high latency 

D. packets in a flow traversing multiple paths through the network 

E. some packets in a flow being process-switched and others being interrupt-switched on a transit router 

Answer: D,E 

Explanation: 

In traditional packet forwarding systems, using different paths have varying latencies that cause out of order packets, eventually resulting in far lower performance for the network application. Also, if some packets are process switched quickly by the routing engine of the router while others are interrupt switched (which takes more time) then it could result in out of order packets. The other options would cause packet drops or latency, but not out of order packets. 

Q256. Which command do you use to connect a dense-mode domain to a sparse-mode multicast domain? 

A. none, because there is no such command 

B. ip pim spt-threshold infinity 

C. ip pim register dense-mode 

D. ip pim dense-mode proxy-register 

Answer:

Explanation: 

For IP PIM multicast, Cisco recommends Sparse-Mode over Dense-Mode. In the midst of our network migration, we have a new network operating in Sparse-Mode with Anycast rendezvous point (RP) but our existing network is still operating in Dense-Mode. To bridge two different modes across both PIM domains, we should use the ip pim dense-mode proxy-register command on the interface leading toward the bordering dense mode region. This configuration will enable the border router to register traffic from the dense mode region (which has no concept of registration) with the RP in the sparse mode domain. 

Reference: http://networkerslog.blogspot.com/2010/12/bridging-dense-mode-pim-to-sparse-mode.html 

Q257. DRAG DROP 

Drag and drop the MPLS term on the left to the function it performs on the right. 

Answer: 

Q258. DRAG DROP 

Drag and drop each step of the Unicast RPF process on the left into the correct order on the right. 

Answer: 

Q259. Which two statements about SNMP traps are true? (Choose two.) 

A. They are sent by an agent after a specified event. 

B. They are sent when solicited after a specified event. 

C. They are equivalent to a community string. 

D. They provide solicited data to the manager. 

E. They are sent by a management station to an agent. 

F. Vendor-specific traps can be configured. 

Answer: A,F 

Explanation: 

The SNMP agent contains MIB variables whose values the SNMP manager can request or change. A manager can get a value from an agent or store a value into the agent. The agent gathers data from the MIB, the repository for information about device parameters and network data. The agent can also respond to a manager's requests to get or set data. An agent can send unsolicited traps to the manager. Traps are messages alerting the SNMP manager to a condition on the network. Traps can mean improper user authentication, restarts, link status (up or down), MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other significant events. 

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_55_se/configuration/guide/scg_2960/swsnmp.html 

Q260. For which two conditions is Cisco Express Forwarding recursion disabled by default when the BGP Prefix Independent Convergence functionality is enabled? (Choose two.) 

A. next hops learned with a /24 mask 

B. next hops learned with any mask shorter than /32 

C. next hops learned with a /32 mask 

D. next hops that are directly connected 

Answer: C,D 

Explanation: 

Recursion is the ability to find the next longest matching path when the primary path goes down. When the BGP PIC feature is not installed, and if the next hop to a prefix fails, Cisco Express Forwarding finds the next path to reach the prefix by recursing through the FIB to find the next longest matching path to the prefix. This is useful if the next hop is multiple 

hops away and there is more than one way of reaching the next hop. 

However, with the BGP PIC feature, you may want to disable Cisco Express Forwarding recursion for the following reasons: 

. Recursion slows down convergence when Cisco Express Forwarding searches all the FIB entries. 

. BGP PIC Edge already precomputes an alternate path, thus eliminating the need for Cisco Express Forwarding recursion. 

When the BGP PIC functionality is enabled, Cisco Express Forwarding recursion is disabled by default for two conditions: 

. For next hops learned with a /32 network mask (host routes) 

. For next hops that are directly connected 

For all other cases, Cisco Express Forwarding recursion is enabled. 

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-bgp-mp-pic.html