All About Virtual 400-101 vce

Answer: B 

Explanation: 

To install a backup path into the forwarding table and provide prefix independent convergence (PIC) in case of a PE-CE link failure, use the additional-paths install backup command in an appropriate address family configuration mode. To prevent installing the backup path, use the no form of this command. To disable prefix independent convergence, use the disable keyword. 

Reference: http://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r4-2/routing/command/reference/b_routing_cr42crs/b_routing_cr42crs_chapter_01.html 

Answer: A,B,C 

Answer: B 

Explanation: 

Locator ID Separation Protocol (LISP) is a network architecture and protocol that implements the use of two namespaces instead of a single IP address: 

. Endpoint identifiers (EIDs)—assigned to end hosts. 

. Routing locators (RLOCs)—assigned to devices (primarily routers) that make up the global routing system. The public networks use the RLOC to forward traffic between networks. 

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_lisp/configuration/15-mt/irl-15-mt-book/irl-overview.html 

Answer: A 

Explanation: 

SRR is scheduling service for specifying the rate at which packets are dequeued. With SRR there are two modes, shaped and shared. Shaped mode is only available on the egress queues SRR differs from typical WRR. With WRR queues are serviced based on the weight. Q1 is serviced for weight 1 period of time, Q2 is served for weight 2 period of time, and so forth. 

The servicing mechanism works by moving from queue to queue and services them for the weighted amount of time. With SRR weights are still followed; however, SRR services Q1, moves to Q2, then Q3 and Q4 in a different way. It does not wait at and service each queue for a weighted amount of time before moving on to the next queue. Instead, SRR makes several rapid passes at the queues; in each pass, each queue might or might not be serviced. For each given pass, the more highly weighted queues are more likely to be serviced than the lower priority queues. 

Reference: http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-3560-e-series-switches/prod_qas0900aecd805bacc7.html 

Answer: A,B,D 

Explanation: 

QoS Features That Require CEF 

These class-based QoS features are supported only on routers that run CEF. 

.Network Based Application Recognition (NBAR) provides intelligent network classification. For more information, refer to Network Based Application Recognition. 

. The AutoQoS -VoIP feature simplifies and speeds up the implementation and provisioning of QoS for VoIP traffic. This feature is enabled with the help of the auto qos voip command. CEF must be enabled at the interface or ATM PVC before the auto qos command can be used. For more information about this feature and its prerequisites, refer to AutoQoS -VoIP. 

From MPLS Fundamentals - Luc De Ghein 

Why Is CEF Needed in MPLS Networks? 

Concerning MPLS, CEF is special for a certain reason; otherwise, this book would not explicitly cover it. Labeled packets that enter the router are switched according to the label forwarding information base (LFIB) on the router. IP packets that enter the router are switched according to the CEF table on the router. Regardless of whether the packet is switched according to the LFIB or the CEF table, the outgoing packet can be a labeled packet or an IP packet 

Reference: http://www.cisco.com/c/en/us/support/docs/asynchronous-transfer-mode-atm/ip-to-atm-class-of-service/4800-cefreq.html 

Answer: A 

Explanation: 

With route poisoning, when a router detects that one of its connected routes has failed, the router will poison the route by assigning an infinite metric to it and advertising it to neighbors. 

Answer: D 

Explanation: 

The ABR for the NSSA generates the default route, but not by default. To force the ABR to generate the default route, use the area <area id> nssa default-information originate command. The ABR generates a Type 7 LSA with the link-state ID 0.0.0.0 and is advertised inside the NSSA. This default route will be propagated inside the NSSA as Type 7 LSA 

Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13692-21.html#nssas 

Answer: A 

Answer: D,E 

Explanation: 

Output drops are caused by a congested interface. For example, the traffic rate on the outgoing interface cannot accept all packets that should be sent out, or a service policy is applied that is oversubscribed. The ultimate solution to resolve the problem is to increase the line speed. However, there are ways to prevent, decrease, or control output drops when you do not want to increase the line speed. You can prevent output drops only if output drops are a consequence of short bursts of data. If output drops are caused by a constant high-rate flow, you cannot prevent the drops. However, you can control them. 

Reference: http://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/6343-queue-drops.html 

Answer: B 

Explanation: 

“mtrace” is a diagnostic tool to trace the multicast path from a specified source to a destination for a multicast group. It runs over IGMP protocol. Mtrace uses any information available to it to determine a previous hop to forward the trace towards the source. 

Reference: http://www.brocade.com/downloads/documents/html_product_manuals/NI_05500c_MULTI CAST/wwhelp/wwhimpl/common/html/wwhelp.htm#context=NI_MCAST&file=IP_Multicast. 3.04.html