2014 Latest Cisco 350-001 Dump Free Download(91-100)!
QUESTION 91
Which of these correctly identifies a difference between the way BPDUs are handled by 802.1w
and 802.1D?
A. 802.1D bridges do not relay BPDUs.
B. 802.1w bridges do not relay BPDUs.
C. 802.1D bridges only relay BPDUs received from the root.
D. 802.1w bridges only relay BPDUs received from the root.
Answer: C
Explanation:
A bridge sends a BPDU frame using the unique MAC address of the port itself as a source address, and a destination address of the STP multicast address 01:80:C2:00:00:00.
There are three types of BPDUs:
Configuration BPDU (CBPDU), used for Spanning Tree computation Topology Change Notification (TCN) BPDU, used to announce changes in the network topology Topology Change Notification Acknowledgment (TCA)
BPDU are Sent Every Hello-Time
BPDU are sent every hello-time, and not simply relayed anymore. With 802.1D, a non-root bridge only generates BPDUs when it receives one on the root port. In fact, a bridge relays BPDUs more
than it actually generates them. This is not the case with 802.1w. A bridge now sends a BPDU with its current information every <hello-time> seconds (2 by default), even if it does not receive any from the root bridge.
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtm l#topic4
QUESTION 92
NBAR supports all of these with the exception of which one?
A. HTTP
B. IP multicast
C. TCP flows with dynamically assigned port numbers
D. non-UDP protocols
Answer: B
Explanation:
Restrictions for Using NBAR
NBAR does not support the following:
More than 24 concurrent URLs, hosts, or Multipurpose Internet Mail Extension (MIME) type matches.
Matching beyond the first 400 bytes in a packet payload in Cisco IOS releases before Cisco IOS Release 12.3 (7)T. In Cisco IOS Release 12.3(7)T, this restriction was removed, and NBAR now supports full payload inspection. The only exception is that NBAR can inspect custom protocol traffic for only 255 bytes into the payload.
Non-IP traffic
Multiprotocol Label Switching (MPLS)-labeled packets – NBAR classifies IP packets only. You can, however, use NBAR to classify IP traffic before the traffic is handed over to MPLS. Use the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC) to set the IP differentiated services code point (DSCP) field on the NBAR-classified packets and make MPLS map the DSCP setting to the MPLS experimental (EXP) setting inside the MPLS header. Multicast and other non-CEF switching modes Fragmented packets Pipelined persistent HTTP requests
URL/host/MIME classification with secure HTTP
Asymmetric flows with stateful protocols
Packets that originate from or that are destined to the router running NBAR NBAR is not supported on the following logical interfaces:
Fast EtherChannel
Dialer interfaces until Cisco IOS Release 12.2(4) T
Interfaces where tunneling or encryption is used
QUESTION 93
Modified deficit round robin supports which of these functionalities?
A. priority queue
B. weighted fair queues
C. round-robin service of output queues
D. LLQ
Answer: AC
Explanation:
Modified deficit round robin (MDRR)–MDRR, a traffic class prioritization mechanism used only on GSR platforms, incorporates emission priority as a facet of quality of service. MDRR is similar in function to WFQ on non-GSR platforms.
In MDRR, IP traffic is mapped to different classes of service queues. A group of queues is assigned to each traffic destination. On the transmit side of the platform, a group of queues is defined on a per- interface basis; on the receive side of the platform, a group of queues is defined on a per-destination basis. IP packets are then mapped to these queues, based on their IP precedence value. These queues are serviced on a round-robin basis, except for a queue that has been defined to run in either of two ways: a) strict priority mode, or b) alternate priority mode. In strict priority mode, the high priority queue is serviced whenever it is not empty; this ensures the lowest possible delay for high priority traffic. In this mode, however, the possibility exists that other traffic might not be serviced for long periods of time if the high priority queue is consuming most of the available bandwidth.
In alternate priority mode, the traffic queues are serviced in turn, alternating between the high priority queue and the remaining queues.
http://www.cisco.com/en/US/docs/ios/12_0st/12_0st10/feature/guide/10st_cos.pdf
QUESTION 94
A router is connected to an HDLC circuit via a T1 physical interface. The SLA for this link only allows for a sustained rate of 768 kb/s. Bursts are allowed for up to 30 seconds at up to line rate, with a window Tc of 125 ms. What should the Bc and Be setting be when using generic traffic
shaping?
A. Be = 46320000 , Bc = 96000
B. Be = ,768000 Bc = 32000
C. Be = ,128000 Bc = 7680
D. Be = ,0 Bc = 96000
Answer: A
Explanation:
Tc= 125
CIR = 768
What is the Be
T1 = 1.544 Mbps
Bursts are allowed for 30 seconds
Seconds * Bandwidth in bps = Be
30 * 1544000 = Be
30 * 1544000 = 46320000
Be = 46320000
What is Bc?
Bc = Tc * CIR
Bc = 125 * 768
Bc = 96000
Traffic Shaping Parameters
We can use the following traffic shaping parameters:
CIR = committed information rate (= mean time)
EIR = excess information rate
TB = token bucket (= Bc + Be)
Bc = committed burst size (= sustained burst size)
Be = excess burst size
DE = discard eligibility
Tc = measurement interval
AR = access rate corresponding to the rate of the physical interface (so if you use a T1, the AR is approximately 1.5 Mbps).
Committed Burst Size (Bc)
The maximum committed amount of data you can offer to the network is defined as Bc. Bc is a measure for the volume of data for which the network guarantees message delivery under normal conditions. It is measured during the committed rate Tc.
Excess Burst Size (Be)
The number of non-committed bits (outside of CIR) that are still accepted by the Frame Relay switch but are marked as eligible to be discarded (DE). The token bucket is a ‘virtual’ buffer. It contains a number of tokens, enabling you to send a limited amount of data per time interval. The token bucket is filled with Bc bits per Tc.
The maximum size of the bucket is Bc + Be. If the Be is very big and, if at T0 the bucket is filled with Bc + Be tokens, you can send Bc + Be bits at the access rate. This is not limited by Tc but by the time it takes to send the Be. This is a function of the access rate.
Committed Information Rate (CIR)
The CIR is the allowed amount of data which the network is committed to transfer under normal conditions. The rate is averaged over a increment of time Tc. The CIR is also referred to as the minimum acceptable throughput. Bc and Be are expressed in bits, Tc in seconds, and the access rate and CIR in bits per second.
Bc, Be, Tc and CIR are defined per data-link connection identifier (DLCI). Due to this, the token bucket filter controls the rate per DLCI. The access rate is valid per user-network interface. For Bc, Be and CIR incoming and outgoing values can be distinguished. If the connection is symmetrical, the values in both directions are the same. For permanent virtual circuits, we define incoming and outgoing Bc, Be and CIR at subscription time.
Peak = DLCI’s maximum speed. The bandwidth for that particular DLCI.
Tc = Bc / CIR
Peak = CIR + Be/Tc = CIR (1 + Be/Bc)
If the Tc is one second then:
Peak = CIR + Be = Bc + Be
http://www.cisco.com/warp/public/125/21.pdf
QUESTION 95
Which of these tables is used by an LSR to perform a forwarding lookup for a packet destined to
an address within an RFC 4364 VPN?
A. CEF
B. FIB
C. LFIB
D. IGP
Answer: C
Explanation:
Notice: The term Label Switch Router (LSR) refers to any router that has awareness of MPLS labels Label Forwarding Information Base (LFIB) is responsible for forwarding incoming packets based on label as it holds necessary label information, as well as the outgoing interface and next-hop information
QUESTION 96
Which two of these parameters are used to determine a forwarding equivalence class? (Choose
two.)
A. IP prefix
B. Layer 2 circuit
C. RSVP request from CE for bandwidth reservation
D. BGP MED value
Answer: AB
Explanation:
A Forwarding Equivalence Class (FEC) is a class of packets that should be forwarded in the same manner (i.e. over the same path). A FEC is not a packet, nor is it a label. A FEC is a logical entity created by the router to represent a class (category) of packets. When a packet arrives at the ingress router of an MPLS domain, the router parses the packet’s headers, and checks to see if the packet matches a known FEC (class). Once the matching FEC is determined, the path and outgoing label assigned to that FEC are used to forward the packet.
FECs are typically created based on the IP destinations known to the router, so for each different destination a router might create a different FEC, or if a router is doing aggregation, it might represent multiple destinations with a single FEC (for example, if those destinations are reachable through the same immediate next hop anyway). The MPLS framework, however, allows for the creation of FECs using advanced criteria like source and destination address pairs, destination address and TOS, etc.
QUESTION 97
A network is composed of several VRFs. It is required that VRF users VRF_A and VRF_B be able
to route to and from VRF_C, which hosts shared services. However, traffic must not be allowed to flow between VRF_A and VRF_B. How can this be accomplished?
A. route redistribution
B. import and export using route descriptors
C. import and export using route targets
D. Cisco MPLS Traffic Engineering
Answer: C
Explanation:
An MPLS VPN implementation is very similar to a dedicated router peer-to-peer model implementation. From a CE router’s perspective, only IPv4 updates, as well as data, are forwarded to the PE router. The CE router does not need any specific configuration to enable it to be a part of a MPLS VPN domain. The only requirement on the CE router is a routing protocol (or a static/default route) that enables the router to exchange IPv4 routing information with the connected PE router. In the MPLS VPN implementation, the PE router performs multiple functions. The PE router must first be capable of isolating customer traffic if more than one customer is connected to the PE router. Each customer, therefore, is assigned an independent routing table similar to a dedicated PE router in the initial peer-to-peer discussion. Routing across the SP backbone is performed using a routing process in the global routing table. P routers provide label switching between provider edge routers and are unaware of VPN routes. CE routers in the customer network are not aware of the P routers and, thus, the internal topology of the SP network is transparent to the customer The P routers are only responsible for label switching of packets. They do not carry VPN routes and do not participate in MPLS VPN routing. The PE routers exchange IPv4 routes with connected CE routers using individual routing protocol contexts. To enable scaling the network to large number of customer VPNs, multiprotocol BGP is configured between PE routers to carry customer routes. Customer isolation is achieved on the PE router by the use of virtual routing tables or instances, also called virtual routing and forwarding tables/instances (VRFs). In essence, it is similar to maintaining multiple dedicated routers for customers connecting into the provider network. The function of a VRF is similar to a global routing table, except that it contains all routes pertaining to a specific VPN versus the global routing table. The VRF also contains a VRF-specific CEF forwarding table analogous to the global CEF table and defines the connectivity requirements and protocols for each customer site on a single PE router. The VRF defines routing protocol contexts that are part of a specific VPN as well as the interfaces on the local PE router that are part of a specific VPN and, hence, use the VRF. The interface that is part of the VRF must support CEF switching. The number of interfaces that can be bound to a VRF is only limited by the number of interfaces on the router, and a single interface (logical or physical) can be associated with only one VRF. The VRF contains an IP routing table analogous to the global IP routing table, a CEF table, list of interfaces that are part of the VRF, and a set of rules defining routing protocol exchange with attached CE routers (routing protocol contexts). In addition, the VRF also contains VPN identifiers as well as VPN membership information (RD and RT are covered in the next section).
Route targets (RTs) are additional identifiers used in the MPLS VPN domain in the deployment of MPLS VPN that identify the VPN membership of the routes learned from that particular site. RTs are implemented by the use of extended BGP communities in which the higher order 16 bits of the BGP extended community (64 total bits) are encoded with a value corresponding to the VPN membership of the specific site. When a VPN route learned from a CE router is injected into VPNv4 BGP, a list of VPN route target extended community attributes is associated with it. The export route target is used in identification of VPN membership and is associated to each VRF. This export route target is appended to a customer prefix when it is converted to a VPNv4 prefix by the PE router and propagated in MP-BGP updates. The import route target is associated with each VRF and identifies the VPNv4 routes to be imported into the VRF for the specific customer. The format of a RT is the same as an RD value.
QUESTION 98
Which of these statements best describes the major difference between an IPv4-compatible tunnel
and a 6to4 tunnel?
A. An IPv4-compatible tunnel is a static tunnel, but an 6to4 tunnel is a semiautomatic tunnel.
B. The deployment of a IPv4-compatible tunnel requires a special code on the edge routers, but a
6to4 tunnel does not require any special code.
C. An IPv4-compatible tunnel is typically used only between two IPv6 domains, but a 6to4 tunnel is
used to connect to connect two or more IPv6 domains.
D. For an IPv4-compatible tunnel, the ISP assigns only IPv4 addresses for each domain, but for a
6to4 tunnel, the ISP assigns only IPv6 addresses for each domain.
Answer: C
Explanation:
Automatic 6to4 Tunnels
An automatic 6to4 tunnel allows isolated IPv6 domains to be connected over an IPv4 network to remote IPv6 networks. The key difference between automatic 6to4 tunnels and manually configured tunnels is that the tunnel is not point-to-point; it is point-to-multipoint. In automatic 6to4 tunnels, routers are not configured in pairs because they treat the IPv4 infrastructure as a virtual nonbroadcast multi-access (NBMA) link. The IPv4 address embedded in the IPv6 address is used to find the other end of the automatic tunnel.
An automatic 6to4 tunnel may be configured on a border router in an isolated IPv6 network, which creates a tunnel on a per-packet basis to a border router in another IPv6 network over an IPv4 infrastructure. The tunnel destination is determined by the IPv4 address of the border router extracted from the IPv6 address that starts with the prefix 2002::/16, where the format is 2002:border-router-IPv4-address::/48. Following the embedded IPv4 address are 16 bits that can be used to number networks within the site. The border router at each end of a 6to4 tunnel must support both the IPv4 and IPv6 protocol stacks. 6to4 tunnels are configured between border routers or between a border router and a host.
The simplest deployment scenario for 6to4 tunnels is to interconnect multiple IPv6 sites, each of which has at least one connection to a shared IPv4 network. This IPv4 network could be the global Internet or a corporate backbone. The key requirement is that each site have a globally unique IPv4 address; the Cisco IOS software uses this address to construct a globally unique 6to4/48 IPv6 prefix. As with other tunnel mechanisms, appropriate entries in a Domain Name System (DNS) that map between hostnames and IP addresses for both IPv4 and IPv6 allow the applications to choose the required address. Automatic IPv4-Compatible IPv6 Tunnels Automatic IPv4-compatible tunnels use IPv4-compatible IPv6 addresses. IPv4-compatible IPv6 addresses are IPv6 unicast addresses that have zeros in the high-order 96 bits of the address, and an IPv4 address in the low-order 32 bits. They can be written as 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D, where “A.B.C.D” represents the embedded IPv4 address.
The tunnel destination is automatically determined by the IPv4 address in the low-order 32 bits of IPv4- compatible IPv6 addresses. The host or router at each end of an IPv4-compatible tunnel must support both the IPv4 and IPv6 protocol stacks. IPv4-compatible tunnels can be configured between border- routers or between a border-router and a host. Using IPv4-compatible tunnels is an easy method to create tunnels for IPv6 over IPv4, but the technique does not scale for large networks.
QUESTION 99
Which information is carried in an OSPFv3 intra-area-prefix LSA?
A. IPv6 prefixes
B. link-local addresses
C. solicited node multicast addresses
D. IPv6 prefixes and topology information
Answer: A
QUESTION 100
Which IPv6 address would you ping to determine if OSPFv3 is able to send and receive unicast
packets across a link?
A. anycast address
B. site-local multicast
C. global address of the link
D. unique local address
E. link-local address
Answer: E
Explanation:
A link-local address is an Internet Protocol address that is intended only for communications within the segment of a local network (a link) or a point-to-point connection that a host is connected to. Routers do not forward packets with link-local addresses.
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