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Q101. Which statement about MSS is true? 

A. It is negotiated between sender and receiver. 

B. It is sent in all TCP packets. 

C. It is 20 bytes lower than MTU by default. 

D. It is sent in SYN packets. 

E. It is 28 bytes lower than MTU by default. 

Answer: D 

Explanation: 

The maximum segment size (MSS) is a parameter of the Options field of the TCP header that specifies the largest amount of data, specified in octets, that a computer or communications device can receive in a single TCP segment. It does not count the TCP header or the IP header. The IP datagram containing a TCP segment may be self-contained within a single packet, or it may be reconstructed from several fragmented pieces; either way, the MSS limit applies to the total amount of data contained in the final, reconstructed TCP segment. The default TCP Maximum Segment Size is 536. Where a host wishes to set the maximum segment size to a value other than the default, the maximum segment size is specified as a TCP option, initially in the TCP SYN packet during the TCP handshake. The value cannot be changed after the connection is established. 

Reference: http://en.wikipedia.org/wiki/Maximum_segment_size 


Q102. 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 


Q103. Which two statements about the metric-style wide statement as it applies to route redistribution are true? (Choose two.) 

A. It is used in IS-IS. 

B. It is used in OSPF. 

C. It is used in EIGRP. 

D. It is used for accepting TLV. 

E. It is used in PIM for accepting mroutes. 

F. It is used for accepting external routes. 

Answer: A,D 

Explanation: 

To configure a router running IS-IS to generate and accept only new-style TLVs (TLV stands for type, length, and value object), use the metric-style wide command. 

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/TE_1208S.html#wp49409 


Q104. Refer to the exhibit. 


Which statement is true? 

A. There is no issue with forwarding IPv6 traffic from this router. 

B. IPv6 traffic can be forwarded from this router, but only on Ethernet1/0. 

C. IPv6 unicast routing is not enabled on this router. 

D. Some IPv6 traffic will be blackholed from this router. 

Answer: D 

Explanation: 

Here we see that the IPV6 default route shows two different paths to take, one via Ethernet 1/0 and one via Ethernet 0/0. However, only Eth 1/0 shows a next hop IPV6 address (the link local IPV6 address). There is no link local next hop addressed known on Eth 0/0. Therefore, traffic to all destinations will be load balanced over the two paths, but only half of the IPv6 traffic will be sent to the correct upstream router. 


Q105. 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: D 

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 


400-101  answers

Up to date 400-101 ccie written exam number:

Q106. DRAG DROP 

Drag and drop the multicast protocol or feature on the left to the correct address space on the right. 


Answer: 



Q107. Which statement is true regarding UDLD and STP timers? 

A. The UDLD message timer should be two times the STP forward delay to prevent loops. 

B. UDLD and STP are unrelated features, and there is no relation between the timers. 

C. The timers need to be synced by using the spanning-tree udld-sync command. 

D. The timers should be set in such a way that UDLD is detected before the STP forward delay expires. 

Answer: D 

Explanation: 

UDLD is designed to be a helper for STP. Therefore, UDLD should be able to detect an unidirectional link before STP would unblock the port due to missed BPDUs. Thus, when you configure UDLD timers, make sure your values are set so that unidirectional link is detected before “STP MaxAge + 2xForwardDelay” expires. 

Reference: http://blog.ine.com/tag/stp/ 


Q108. 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/ 


Q109. When deploying redundant route reflectors in BGP, which attribute can you configure on the route reflector to allow routes to be identified as belonging to the same group? 

A. ROUTER_ID 

B. CLUSTER_ID 

C. ORIGINATOR_ID 

D. PEER_GROUP 

Answer: B 

Explanation: 

Together, a route reflector and its clients form a cluster. When a single route reflector is deployed in a cluster, the cluster is identified by the router ID of the route reflector. The bgp cluster-id command is used to assign a cluster ID to a route reflector when the cluster has one or more route reflectors. Multiple route reflectors are deployed in a cluster to increase redundancy and avoid a single point of failure. When multiple route reflectors are configured in a cluster, the same cluster ID is assigned to all route reflectors. This allows all route reflectors in the cluster to recognize updates from peers in the same cluster and reduces the number of updates that need to be stored in BGP routing tables. 

Reference: http://ieoc.com/forums/t/5326.aspx 


Q110. Refer to the exhibit. 


Which two statements about the implementation are true? (Choose two.) 

A. The PPP multilink protocol header is omitted on delay-sensitive packets. 

B. The maximum number of fragments is 1. 

C. Small real-time packets are multilink-encapsulated. 

D. A transmit queue is provided for smaller packets. 

Answer: A,D 

Explanation: 

Previous implementations of Cisco IOS Multilink PPP (MLP) include support for Link Fragmentation Interleaving (LFI). This feature allows the delivery of delay-sensitive packets, such as the packets of a Voice call, to be expedited by omitting the PPP Multilink Protocol header and sending the packets as raw PPP packets in between the fragments of larger data packets. This feature works well on bundles consisting of a single link. However, when the bundle contains multiple links there is no way to keep the interleaved packets in sequence with respect to each other. The Multiclass Multilink PPP (MCMP) feature in Cisco IOS Release 12.2(13)T addresses the limitations of MLP LFI on bundles containing multiple links by introducing multiple data classes. With multiclass multilink PPP interleaving, large packets can be multilink-encapsulated and fragmented into smaller packets to satisfy the delay requirements of real-time voice traffic; small real-time packets, which are not multilink encapsulated, are transmitted between fragments of the large packets. The interleaving feature also provides a special transmit queue for the smaller, delay-sensitive packets, enabling them to be transmitted earlier than other flows. Interleaving provides the delay bounds for delay-sensitive voice packets on a slow link that is used for other best-effort traffic. 

References: http://www.cisco.com/c/en/us/td/docs/ios/dial/configuration/guide/12_4t/dia_12_4t_book/dia _multiclass_link_ppp.pdf http://www.cisco.com/c/en/us/td/docs/routers/access/500/520/software/configuration/guide/520_SCG_Book/520scg_concepts.html