MPLS quiz

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Question

Answer

Hint

How many bytes are in a MPLS packet?

4 Bytes

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What layer is the MPLS packet header inserted in the IP packet?

Between layers 2 and 3

Called the Shim Header

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What label is used to signal Operation and Maintenance (OAM) used for failure detection, localization and performance monitoring?

OAM Alert – label 14

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When packets enter the network, the ingress router determines the __________ .

Forwarding Equivalence Class (FEC)

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The ingress LER identifies the egress LER and sends it down the corresponding _______.

LSP Label Switch Path

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True or False A data packet can have multiple MPLS labels

True

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What are the two types of MPLS labels?

Transport and Inner

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How are the transport labels learned by the MPLS enabled routers?

LDP or RSVP

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MPLS EXP field is used for QoS, How many bits are in the EXP field?

only 8 class QoS

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If your MPLS network is using more than 8 classes, How are additional bit acquired to gain additional classes?

Using the Most significant bits in the part of the label field (L-LSP)

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What are the two MPLS modes?

Cell and Frame

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In _________ mode, Routers exchange pure MPLS and IP packets.

Frame Mode

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TRue or False: LDP exchanges messages between peers or also known as neighbors

True

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LDP Neighbors are point-to-point and discovered via hello _________ messages 224.0.0.2 to a well known UDP port ___.

Multicast,646

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Remote LDP peers or peers that are not directly connected can also be discovered with unicast UDP _______ hellos

targeted

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True or False: If pair of peers directly connected have more then one interface between each other there are multiple LDP sessions established.

False

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LDP uses ___ for reliable delivery and session health

TCP

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The ____ must converge for LDP to converge

IGP

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What are the two label retention modes in MPLS?

liberal and conservative

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label mapping advertisements for all routes may be received from all LDP peers.

Unsolicited Downstream label distribution mode

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each LSR may advertise label mapping to its neighbors at any time it desires

Independent LSP Control

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What protocols does MPLS TE leverage to distribute additional information about the network such as? Available bandwidth per interface by priority, Attribute flags per interface, Administrative weight per interface.

OSPF or IS-IS

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What routing protocols support MPLS TE?

OSPF with LSA type 10and IS-IS with sub-TLV 250 and 251

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True or False: MPLS TE reserves bandwidth on a per tunnel basis.

True

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MPLS TE tunnels have two types of priorities both using 0-7 with the lower number the being the best number. What are the 2 priority types?

setup,hold

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True or False: MPLS TE tunnels can have a setup priority better than its hold priority.

false

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The attribute flag of a link contains how many bits?

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What metric are used to route MPLS TE traffic?

attributes, administrative weight, weight

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When does MPLS TE flood information to all other routers?

links goes up or downLink’s configurations changes, when it’s time to periodically re-flood, link bandwidth changes significantly

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RSVP is considered a ________ protocol and requires periodic refresh.

soft state

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What is the default periodic flood time for MPLS TE?

180 seconds

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What method is used to calculate best path in MPLS TE?

constrained SPF

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____________allow for a tunnel to be built based on a series of explicitly defined next hops Include or exclude.

Explicit path-options

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When using RSVP what device is responsible for controlling the LSP?

ingress LER

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If there is an active tunnel up in the network and a better path becomes available the tunnel can be____________ to a new path.

re-optimized

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What protocol provides end to end resource reservations?

RSVP

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RSVP provides what 3 functions?

Path setup and maintenance Path teardown Path signaling

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You want to ensure that your RSVP LSPs are following a particular path across the network. Which RSVP object ensures that your desire will be met? A. explicit route object B. record route object C. session object D. traffic specification object

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Once the Path message reaches the destination it replies with a __________. A. ResvConfirm Message B. Hello Message C. Resv message D. Interserv Flowspec

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A Resv is the acknowledgement that the reservation has been accepted end to end. What mechanism use by the egress tunnel router to signal headend tunnel?

Explicit route order

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The Headend tunnel router sends a Path Message per tunnel to its neighbor every __ seconds? A. 5 B. 10 C. 30 D. 20

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What 2 messages are sent along the path to tear down the tunnel?

PathTer, and ResvTer

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This MPLS TE optional mechanism allows LSPs to share bandwidth with itself.

Shared Explicit Reservation Style.

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This feature of MPLS TE prevents the loss of data during tunnel re-optimization or a change in tunnel parameters.

make before break

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When a MPLE TE tunnel needs to be built across multiple areas or an intra-area tunnel you must use explicate path with _______________ ERO.

Loose

This is used when the headend does not have routing past its own area and must rely on the ARB to complete the LSP tunnel to the egress LER.

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What 3 methods are used to forward traffic down the MPLS tunnels?

static route, policy routing, and autoroute.

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This routing feature of MPLS TE modifies the shortest path tree on the tunnel head-end LSR before the best routes are selected by the SPF. The path toward the tunnel tail-end LSR is replaced by a direct link created by the MPLS TE tunnel in the SPF tree.

autoroute

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This mechanism can be configured on a per-LSP basis that monitor the interface rate and periodically resize the TE tunnel bandwidth.

Auto bandwidth

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MPLS TE has the ability to mitigate packet loss associated with link and node failures using this predefined protection schemes know as ___________.

FRR

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What are the 2 protection schemes that can be implemented with Fast Reroute FRR?

Path protection, Local protection

Local is more scalable

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What are the advantages of Local protection?

Fast failure recovery,1:N scalability,Less consumption of network state

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During a failure the PLR encapsulates the LSP onto the FRR tunnel to the___________.

Nhop

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True or False: When you are using Node Protection of downstream nodes you automatically are protecting the links of the node.

true

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What is the label mechanism is required to make node protection work properly?

ERO

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What is the fast mechanism to determine a link failure with in the network? A. LDP Hellos B. IGP convergence C. RSVP Error detection D. Physical Layer

Physical Layer

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When FRR is implemented and a failure occurs, a PathErr alerts the headend to ____________ the tunnel to find the most optimum path.

re-optimize

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True or False: The IGP is just as effective as MPLS TE FRR in restoring service during a network failure in sub 50ms.

false

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What is a new feature used to enhance the FRR capabilities in the IP/LDP to provide sub 50ms restoration of failures?

Loop Free Alternative

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This most widely used MPLS QoS mechanism is highly scalable and parses data packets at the edge into classes on a per-hop queuing basis.

DifServ

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How many classes does Differentiated Services Code Point (DSCP) support in the IP Packet?

64 classes

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How many classes does the MPLS EXP field support?

8 classes

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In this mode of MPLS QoS the packet classes are inferred based on the EXP field and maps a DSCP value to a EXP class.

EXP-Inferred LSP (E-LSP)

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In this mode of MPLS QoS the packet classes are inferred from the label and the EXP value is ignored.

Label-Only-Inferred LSP (L-LSP)

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An E-LSP is capable of carrying how many classes on a single LSP?

8 Classes

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In the Label Stacking process when going from IP to MPLS, what bits are copied to the EXP Field?

most significant bits

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What are the 3 tunnel modes Tunnel modes that effect which PHB the resulting packets get in MPLS to MPLS or MPLS to IP?

Uniform, Short Pipe, Pipe

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This tunnel mode propagates a copy of any changes made to the EXP value upward and downward.

Uniform Mode

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This tunnel mode will copy the DSCP into EXP on imposition and does not modify the DSCP on exposition.

Short Pipe Mode

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This model guarantees that there are no changes to the tunneled PHB marking through the LSP; even if an LSR along the path performs traffic conditioning and re-marks the traffic.

Pipe Mode

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This extends MPLS traffic engineering to enable you to perform constraint-based routing of "guaranteed" traffic, which satisfies a more restrictive bandwidth constraint than that satisfied by CBR for regular traffic. The more restrictive bandwidth is term

DS-TE

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The service provider network is a connection of point-to-point links or virtual circuits (VCs). Routing within the customer network is transparent to the service provider network, and routing protocols run directly between customer routers.

Overlay model

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Both provider and customer network use the same network protocol and all the customer routes are carried within the core network (service provider network).

Peer to Peer model

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What are the building blocks of the MPLS Layer 3 VPN?

MPLS LDP or RSVP, Virtual Routing and Forwarding (VRF), Route Distinguisher (RD), Route Targets (RT), MP-BGP

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A technology that allows multiple instances of a routing table to co-exist within the same router at the same time and enables different customers to use overlapping addresses.

VRF

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8-octet field prefixed to the customer's Internet Protocol address (IPv4) used by the edge routers to identify which VPN a packet belongs to.

Route Distinguisher

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MPLS based VPNs use____________ protocol to pass routes between PE devices.

BGP

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An 8 byte field used to define the values that should be matched against to decide whether a route is eligible to be imported into this VRF.

Route Target

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This extension called VPNv4 added to this protocol provides MPLS layer 3 route propagation.

MP-BGP

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What protocols supported between PE to CE routers?

Static,RIPv2,OSPF,EIGRP,IS-IS,eBGP

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An __________ can be understood as an intranet mapped onto the public Internet or some other transmission system not accessible to the general public.

Extranet

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How does MPLS Layer 3 VPN’s provide for Extranet support using the?

VRF table import/export

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A full mesh of MP-iBGP sessions is required between the PE routers, This creates scaling issues, but this issue can be alleviated somewhat by using __________ routers.

Route Reflectors

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Many customers require Internet service at some or all of their locations, please list the 3 designs that could provide this connectivity?

Using Central Firewall,Using a separate BGP session Internet routing, Central Internet provider site with a default router.

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This option allows routers to identify the site from which each route originated, the following Routing protocols are supported: OSPF, EIGRP, BGP.

Site of Origin

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When redistributing MP-BGP VPNv4 routes into EIGRP that has multiple connections to the same network, what BGP attribute must be set to prevent loopbacks?

Site of Origin extended community with a route-map

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What is the name of the RFC which gives MPLS providers the ability to efficiently transmit customer multicast traffic.

mVPN

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These trees are built inside the providers and connected using GRE tunnels to distribute content to many users.

Multicast Distribution Tree

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What are the 2 types of Multicast Distribution Tree’s?

Default MDT Groups, Data MDT Group

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What label is used to indicate: Egress LSR request upstream LSR to perform pop

Implicit NULL – label 3

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What are the 3 MPLS Label operations the MPLS routers must perform?

PUSH,SWAP,POP

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What label is used to indicate: Egress LSR request upstream LSR to perform swap?

Explicit NULL – label 0

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Created by: maa4116

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