350-501 Practice Test 44 — 15 Questions

Question 1

A service provider is designing a Layer 2 MPLS VPN to connect multiple customer sites. Which technology should be used to provide end-to-end Ethernet service with MAC address transparency and support for multiple customer VLANs?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

VPLS (Virtual Private LAN Service). VPLS (Virtual Private LAN Service) is the correct choice because it emulates an Ethernet bridge across an MPLS core, providing MAC address transparency and supporting multiple customer VLANs through a multipoint-to-multipoint topology. Unlike point-to-point services, VPLS learns MAC addresses and forwards frames based on them, enabling end-to-end Ethernet service across distributed sites.

Answer

MPLS Traffic Engineering (MPLS TE)

Answer

VPWS (Virtual Private Wire Service)

Answer

RSVP-TE signaling

Question 2

Which TWO statements correctly describe RSVP-TE reservation styles? (Choose two.)

Accepted Answer

Shared Explicit (SE) allows multiple senders to share a reservation but with explicit filters.. Option B is correct because Shared Explicit (SE) is a reservation style in which a single reservation can be shared by multiple senders, but the receiver explicitly lists the senders (explicit filters) that may use that reservation. Option E is correct because Fixed Filter (FF) creates a distinct reservation for each individual sender, with no sharing between senders, and each sender is identified by its own filter spec. Option A is wrong because SE does allow sharing, just with explicit sender selection, so saying it does not allow any sharing is false. Option C is wrong because MPLS-TE supports multiple RSVP-TE reservation styles, not only Fixed Filter. Option D is wrong because Wildcard Filter (WF) is not commonly used in MPLS-TE; MPLS-TE typically uses FF or SE, and WF is more associated with shared reservations without explicit sender lists.

Answer

Shared Explicit (SE) does not allow any sharing.

Answer

Fixed Filter (FF) is the only style used in MPLS-TE.

Answer

Wildcard Filter (WF) is commonly used in MPLS-TE.

Question 3

In Segment Routing over IPv6 (SRv6), what is the function of the 'Locator' part of an SRv6 SID?

Accepted Answer

It identifies the node and is used for routing the packet to that node.. The Locator is the portion of the SRv6 SID that identifies the node (or the segment endpoint) and is used for routing to that node.

Answer

It indicates the length of the SID.

Answer

It encodes an argument for the SRv6 function.

Answer

It specifies the function to be performed on the packet.

Question 4

Which LDP label retention mode stores all received label bindings even if they are not currently used for forwarding?

Accepted Answer

Liberal label retention. Liberal label retention stores all label bindings, allowing quick convergence when a path changes, while conservative retention stores only bindings from the next-hop.

Answer

Conservative label retention

Answer

Ordered label distribution

Answer

Downstream unsolicited

Question 5

Which SR-MPLS SID is advertised by an IS-IS router to identify a specific link and is distributed only to adjacent neighbors?

Accepted Answer

Adjacency SID. An Adjacency SID in SR-MPLS is a local SID advertised by an IS-IS router to identify a specific adjacency (link) to a neighbor. It is distributed only to directly adjacent neighbors and is used for hop-by-hop forwarding and traffic engineering. Prefix SIDs, by contrast, are advertised network-wide to identify a prefix.

Answer

Prefix SID

Answer

Node SID

Answer

Anycast SID

Question 6

Which two statements about MPLS label operations are true? (Choose two.)

Accepted Answer

Push operation adds a label to the packet.. Option C is correct because the push operation inserts a new MPLS shim header (label) onto the packet's label stack at the ingress LER, encapsulating the IP packet with the label imposed by the forwarding entry. Option E is correct because the pop operation removes the top label from the stack, and when a router receives the reserved implicit-null label (value 3), it pops that label and forwards the packet as a plain IP packet to the adjacent router. Option A is incorrect because push can add more than one label at a time (e.g., label stacking for MPLS VPNs or TE), not strictly one. Option B is incorrect because a pop operation removes only the top label per operation; removing multiple labels requires multiple pops or a PHP-style action, not a single multi-label pop. Option D is incorrect because swap replaces the top label with a new label (one-for-one), it does not remove and replace two labels.

Answer

Push operation can only add one label at a time.

Answer

Pop operation can remove multiple labels at once.

Answer

Swap operation removes and replaces two labels.

Question 7

A service provider wants to provide Layer 3 VPN services to customers using MPLS. Which technology is used to distribute VPNv4 routes between PE routers?

Accepted Answer

MP-BGP. MP-BGP (Multiprotocol BGP) is the routing protocol used to distribute VPNv4 routes between PE routers in an MPLS Layer 3 VPN. It carries the route target and route distinguisher extended communities that identify which VPN a prefix belongs to. Standard IGPs like OSPF or IS-IS cannot carry the VPNv4 address family or the required BGP extended communities.

Answer

IS-IS

Answer

OSPF

Answer

EIGRP

Question 8

An SP network is running OSPFv3 for IPv6 and needs to support traffic engineering extensions for RSVP-TE. Which three statements about OSPFv3 TE extensions are true?

Accepted Answer

OSPFv3 TE uses TLV 1 (Router Address) in Opaque LSAs.. OSPFv3 uses Opaque LSA types 9, 10, and 11 for TE, with Type 10 carrying TE information link-state. OSPFv3 TE requires the OSPFv3 process to be configured for TE.

Answer

OSPFv3 TE requires the use of wide metrics.

Answer

OSPFv3 TE only supports point-to-point links.

Question 9

An SP wants to filter BGP prefixes received from a customer to prevent hijacking. Which two tools can be used together on the provider edge router to implement inbound prefix filtering?

Accepted Answer

Prefix-list and route-map. Prefix-lists and route-maps are commonly used together to match and filter BGP prefixes. Prefix-lists define the prefixes, and route-maps apply them in BGP neighbor statements.

Answer

Distribute-list and ACL

Answer

RPKI and BGP community

Answer

AS-path access-list and community-list

Question 10

A service provider is deploying a BNG for subscriber management. Which protocol is used to authenticate subscribers and assign IP addresses via the BNG?

Accepted Answer

RADIUS. BNG typically uses RADIUS for authentication, authorization, and accounting of subscribers. DHCP server functionality on BNG assigns IP addresses, but authentication is via RADIUS.

Answer

PPPoE only

Answer

LDAP

Answer

TACACS+

Question 11

An SP network operator needs to ensure that voice traffic always gets priority access to the output link. Which queuing mechanism is designed to provide a strict priority queue while preventing starvation of other queues?

Accepted Answer

LLQ. LLQ provides a strict priority queue for EF traffic and includes a policer to limit the priority traffic rate, preventing starvation of other queues.

Answer

CBWFQ

Answer

FIFO

Answer

WRED

Question 12

Which BGP attribute is used to prefer a specific entry point into an AS when multiple ASBRs are advertising the same prefix to a neighboring AS?

Accepted Answer

MED. MED (Multi-Exit Discriminator) is used to influence the inbound traffic by suggesting the preferred entry point.

Answer

LOCAL_PREF

Answer

WEIGHT

Answer

AS_PATH

Question 13

A service provider is designing a Segment Routing over MPLS (SR-MPLS) core. The network architect wants to ensure that the IGP only advertises the loopback prefix with a prefix SID, and that other prefixes do not consume SID space. Which mechanism should be used?

Accepted Answer

Enable the IGP's segment routing capability and assign a prefix SID only to the loopback prefix using an explicit index.. In SR-MPLS, prefix SIDs are assigned to IGP prefixes to create global segments. To ensure only the loopback prefix has a SID, the IGP segment routing capability must be enabled, and then a prefix SID is explicitly assigned to the loopback prefix. This is typically done by configuring a prefix SID with an index under the loopback interface's IGP configuration. Other prefixes are not assigned SIDs, so they do not consume SID space. This design is common in service provider cores to conserve SID resources and simplify the SRGB.

Answer

Use BGP to advertise the loopback prefix with a BGP attribute that carries the SID.

Answer

Configure the IGP to use prefix SIDs only on the loopback interface and disable prefix SIDs globally.

Answer

Configure the IGP to use adjacency SIDs only, avoiding prefix SIDs entirely.

Question 14

An engineer is configuring MPLS L3VPN on a Cisco IOS XR PE router. The customer edge router is connected via a VRF interface. Which of the following is required to enable the PE router to advertise VPN routes to other PE routers?

Accepted Answer

Configure a route distinguisher and route target under the VRF address-family.. To advertise VPN routes in an MPLS L3VPN, the PE router must configure a route distinguisher and route target under the VRF address-family. The RD ensures uniqueness of the customer prefix, and the RT defines the import/export policy. These are then carried in MP-BGP VPNv4 updates to other PE routers. Without these, the PE cannot correctly advertise or import VPN routes, and the L3VPN service will not function.

Answer

Enable OSPF as the PE-CE routing protocol and redistribute into BGP.

Answer

Enable MPLS TE tunnels between PE routers and map customer routes to the tunnels.

Answer

Configure MPLS LDP on the core-facing interfaces and enable BGP IPv4 unicast.

Question 15

A service provider is deploying a Cisco IOS XE router as a PE in an MPLS L3VPN network. The provider wants to offer a managed CE router service where the PE signals QoS information to the CE using BGP. The CE must be able to classify traffic into the correct forwarding class based on the QoS marking received from the PE. Which BGP attribute should the PE set so that the CE can map received traffic to the appropriate class without relying on IP DSCP markings?

Accepted Answer

Set the BGP attribute for QoS using the QoS-marking extended community.. The QoS-marking extended community is the BGP attribute intended to carry QoS information between BGP speakers. By setting it on routes advertised from the PE to the CE, the provider enables the CE to match the community in a route-map and assign the correct forwarding class or QoS group. This decouples classification from packet markings and supports a managed CE service model.

Answer

Set the BGP local-preference attribute to a value that represents the forwarding class.

Answer

Set the BGP MED attribute to match the DSCP value of the traffic.

Answer

Set the BGP extended community for QoS using the color extended community.