350-501 Practice Test 22 — 15 Questions

Question 1

In IS-IS, which metric type supports traffic engineering (TE) and is required for segment routing?

Accepted Answer

Wide metrics (TLV 135/236/22). IS-IS wide metrics (TLV 135/236/22) support TE and segment routing; narrow metrics (TLV 128/130) are limited to 6-bit metrics.

Answer

Default metric (TLV 2)

Answer

Narrow metrics (TLV 128/130)

Answer

TE metric (TLV 138)

Question 2

A service provider wants to use BGP Prefix Independent Convergence (PIC) for faster failover. Which BGP feature must be enabled to support PIC?

Accepted Answer

BGP additional paths. BGP PIC requires BGP additional paths (add-path) or BGP PIC edge, which installs backup paths in the FIB independent of the prefix count.

Answer

BGP multipath

Answer

BGP route reflectors

Answer

BGP fast external fallover

Question 3

An SP engineer is designing an OSPF network and wants to reduce the number of LSAs in a stub area. Which TWO area types would block Type 5 LSAs but allow Type 3 LSAs? (Choose two.)

Accepted Answer

NSSA. Stub and NSSA allow Type 3 LSAs but block Type 5 LSAs. Totally stubby blocks both Type 3 and Type 5.

Answer

Totally stubby area

Answer

Backbone area 0

Answer

Normal area

Question 4

Which OSPF area type is most suitable for a service provider's customer-facing network where external routes are blocked, but internal routes (including inter-area) are allowed, and the area should not accept Type 5 LSAs?

Accepted Answer

Stub area. A stub area blocks Type 5 LSAs but allows inter-area and intra-area routes. It injects a default route. NSSA allows limited external routes via Type 7, which is not desired here.

Answer

NSSA

Answer

Backbone area

Answer

Totally stubby area

Question 5

Which technology allows a service provider to offer different classes of service over a single MPLS network?

Accepted Answer

QoS. QoS (Quality of Service) enables a service provider to differentiate traffic by marking packets with specific DSCP or IP precedence values and applying policies such as policing, shaping, and queuing. This allows multiple classes of service (e.g., voice, video, best-effort) to be carried over a single MPLS network while guaranteeing bandwidth, latency, and jitter requirements for each class.

Answer

BGP

Answer

LDP

Answer

MPLS VPN (VRF)

Question 6

A service provider is implementing network automation using YANG data models. They need to ensure that the automation solution supports both configuration and operational state data retrieval. Which NETCONF operation should be used to retrieve operational state data?

Accepted Answer

. The NETCONF operation retrieves both configuration and operational state data from a device, making it the correct choice for this requirement. Unlike , which only returns configuration data, accesses the running datastore and includes state data such as interface statistics, routing tables, and system status. This aligns with RFC 6241, where is defined as the operation to retrieve combined config and state information.

Answer

<edit-config>

Answer

<get-config>

Answer

<lock>

Question 7

A service provider is deploying Segment Routing over IPv6 (SRv6) and needs to ensure that the forwarding plane can support SRv6 encapsulated packets. Which hardware capability is most critical for SRv6 at the line rate?

Accepted Answer

IPv6 extension header processing. SRv6 (Segment Routing over IPv6) encapsulates packets with an IPv6 header containing a Segment Routing Header (SRH), which is a type of IPv6 extension header. For line-rate forwarding, the hardware must natively process IPv6 extension headers in the forwarding plane without punting to the CPU, as software processing would cause performance degradation. Option C is correct because this capability is the most critical for SRv6 at line rate.

Answer

MPLS label swap capability

Answer

VXLAN tunnel termination

Answer

NAT64 translation support

Question 8

Which MPLS EXP bits value is typically mapped from DSCP EF at the ingress PE to maintain voice QoS in an MPLS network?

Accepted Answer

EXP 5. DSCP EF (46) is commonly mapped to MPLS EXP 5 to preserve priority across the MPLS core.

Answer

EXP 3

Answer

EXP 7

Answer

EXP 0

Question 9

An engineer is configuring EVPN IRB (Integrated Routing and Bridging) to provide IP connectivity between tenants across a service provider network. Which THREE components are essential for EVPN IRB operation? (Choose three.)

Accepted Answer

IP-VRF for each tenant.. EVPN IRB requires an IP-VRF to represent the tenant, a bridge domain (EVI) for Layer 2, and IRB interfaces (Layer 3 gateway) that connect the bridge domain to the VRF. BGP EVPN control plane is also needed.

Answer

LDP or SR for label distribution.

Answer

MPLS-TE tunnels for transport.

Question 10

A service provider is migrating from LDP to SR-MPLS. Which mechanism allows a router to allocate labels for prefixes using both LDP and SR simultaneously during the migration?

Accepted Answer

Segment Routing Mapping Server (SRMS). Cisco's SR/LDP interworking allows coexistence. Routers can run both LDP and SR, and a mapping server advertises SR labels for LDP-learned prefixes. This enables seamless migration.

Answer

LDP over SR tunnel

Answer

RSVP-TE interworking

Answer

MPLS forwarding plane adjustment

Question 11

Which EVPN component ensures that only one of the multi-homed PEs forwards traffic to the CE for a given Ethernet segment?

Accepted Answer

DF Election. DF election determines which PE forwards traffic for a given VLAN to avoid duplication.

Answer

Split Horizon

Answer

Aliasing

Answer

ESI (Ethernet Segment Identifier)

Question 12

What is the primary purpose of the SRGB (Segment Routing Global Block) when configuring SR-MPLS on a network?

Accepted Answer

To provide a common label space for global segments, ensuring consistent label to prefix mapping.. SRGB defines a range of labels reserved for global segments (e.g., Node SIDs). It ensures that a given Node SID maps to the same label across all routers in the SR domain, simplifying operations.

Answer

To set aside labels for MPLS-TE tunnels.

Answer

To allocate labels for adjacency SIDs only.

Answer

To define the range for LDP labels used in SR interworking.

Question 13

An engineer is troubleshooting an MPLS-TE tunnel that is not coming up. The configuration includes an explicit path with strict hops. Which TWO conditions could prevent the tunnel from being established? (Choose two.)

Accepted Answer

RSVP is not enabled on an interface along the path.. An explicit path with strict hops requires each hop to be directly connected. If a hop is not directly connected, the path fails. Also, if there is no RSVP capability along the path, the tunnel cannot be signaled.

Answer

The tunnel interface has an IP address.

Answer

The destination loopback is not advertised in IGP.

Answer

The path includes a router that does not support MPLS.

Question 14

Which three are characteristics of SR-TE policies? (Choose three.)

Accepted Answer

They are defined at the headend router with a destination and color.. SR-TE policies are stateful at the headend, use segment lists for path steering, and can be associated with a color for traffic engineering.

Answer

They require RSVP-TE signaling to maintain state.

Answer

They require per-flow state at intermediate routers.

Question 15

In Segment Routing (SR-MPLS), which IGP TLV is used by IS-IS to advertise the Node SID for a prefix?

Accepted Answer

TLV 135 (Extended IP Reachability) with sub-TLV 3 for Prefix-SID.. IS-IS uses the IS-IS Router CAPABILITY TLV (135) with sub-TLV 19 to carry the SR-capable information and prefix-SID. Specifically, the Prefix-SID is advertised in the IS-IS Extended IP Reachability TLV (135) with sub-TLV 3.

Answer

TLV 22 (IS Reachability) with sub-TLV 22 for Adjacency SID.

Answer

TLV 130 (IP Address) with sub-TLV 1 for Node SID.

Answer

TLV 137 (Dynamic hostname) with sub-TLV 5 for SID.