350-501 Practice Exam 55 — 20 Questions

Question 1

An SP is deploying EVPN with VXLAN encapsulation in a data center interconnect. The design requires that the control plane for MAC/VTEP learning is based on BGP. Which BGP address family must be configured?

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

Accepted Answer

l2vpn evpn. EVPN with VXLAN encapsulation requires the BGP L2VPN address family (l2vpn evpn) to exchange MAC/VTEP reachability information. This address family carries EVPN routes (type-2 for MAC/IP, type-3 for IMET) that populate the control plane for VXLAN tunnel endpoints, enabling MAC learning without flooding.

Answer

l2vpn vpls-vpws

Answer

vpnv4

Answer

ipv4 unicast

Question 2

In an OSPF network, an engineer wants to minimize the size of the routing table in a non-backbone area while still allowing the area to learn external routes from other ASs. Which OSPF area type should be configured?

Accepted Answer

NSSA. A Not-So-Stubby Area (NSSA) allows importing external routes as Type 7 LSAs while still blocking Type 5 LSAs from other areas.

Answer

Stub area

Answer

Totally stubby area

Answer

Backbone area 0

Question 3

In an MPLS L3VPN network, a route reflector (RR) is used to distribute VPNv4 routes between PE routers. After a new PE router (PE4) is added, some VPN routes are not being received by other PEs. Which TWO actions should be investigated to resolve the issue? (Choose two.)

Accepted Answer

Ensure the VRF route-target import/export values are correctly configured on the new PE.. The new PE must have matching VRF route-target import/export values to receive and advertise VPN routes. Option C is correct because a BGP VPNv4 neighbor relationship between the new PE and the RR is necessary for VPNv4 route exchange. Option B is incorrect: OSPF as an additional IGP is not required for VPN route distribution. Option D is incorrect: while physical connectivity and IGP adjacency are prerequisites, the specific issue with missing VPN routes points to BGP session or RT misconfiguration. Option E is incorrect: a route refresh does not fix missing route-target or BGP session problems.

Answer

Configure OSPF as an additional IGP to redistribute VPN routes.

Answer

Check physical connectivity and IGP adjacency between the new PE and the RR.

Answer

Issue a 'clear ip bgp * refresh' on the RR.

Question 4

An engineer configures MPLS TE tunnels. After configuration, the tunnel remains down. The 'show mpls traffic-eng tunnels' output shows 'Tunnel is down - path computation failed'. What is the most likely cause?

Accepted Answer

IGP TE extensions are not enabled on the head-end router.. The 'path computation failed' error indicates that the head-end router cannot find a valid path for the MPLS TE tunnel. IGP TE extensions (OSPF TE or IS-IS TE) must be enabled on the head-end router to flood link attributes (bandwidth, TE metrics) and build the TED (Traffic Engineering Database). Without the TED, CSPF (Constrained Shortest Path First) cannot compute a path, leaving the tunnel down.

Answer

RSVP is not enabled on the head-end router.

Answer

MPLS LDP is not enabled on the head-end router.

Answer

There is an MTU mismatch along the path.

Question 5

Refer to the exhibit. A PE router has this BGP configuration. The CE router is advertising a default route via eBGP. However, the PE is not installing the route in the VRF table. What is the most likely cause?

Accepted Answer

The neighbor 10.1.1.1 is not configured under the address-family ipv4 vrf CUSTOMER. The BGP configuration shows that the neighbor 10.1.1.1 is configured under the BGP IPv4 unicast address-family, but not under the address-family ipv4 vrf CUSTOMER. For a VRF to install a route learned via eBGP from a CE router, the neighbor must be explicitly activated under the VRF address-family. Without this, the PE will receive the default route but will not place it into the VRF routing table.

Answer

The redistribute connected command under the VRF is overwriting the default route

Answer

The next-hop-self under the VRF address-family is not set

Answer

The default-information originate command is missing

Question 6

Which DSCP value is recommended for Expedited Forwarding (EF) per-hop behavior, commonly used for voice traffic?

Accepted Answer

DSCP 46. EF is defined as DSCP 46 (binary 101110) for low-loss, low-latency traffic like voice.

Answer

DSCP 48

Answer

DSCP 34

Answer

DSCP 0

Question 7

An SP is designing a QoS policy for a customer with voice, video, and data traffic. Which queuing mechanism provides a strict priority queue for voice while ensuring other queues do not starve?

Accepted Answer

LLQ. LLQ provides a strict priority queue for real-time traffic (voice) and uses CBWFQ for other data classes with bandwidth guarantees.

Answer

WFQ

Answer

WRED

Answer

CBWFQ

Question 8

Refer to the exhibit. CE1 is not receiving the VPNv4 route for the 192.168.1.0/24 subnet. What is the most likely cause?

Accepted Answer

PE1 is missing the neighbor statement under address-family ipv4 vrf CUSTOMER_A. For CE1 to receive the VPNv4 route for 192.168.1.0/24, PE1 must redistribute the route from the VRF into BGP. The neighbor statement under address-family ipv4 vrf CUSTOMER_A is required to establish an eBGP peering with CE1 and exchange IPv4 routes within that VRF. Without it, PE1 will not send any routes to CE1, even if the VRF and route targets are correctly configured.

Answer

PE1 is missing the VRF configuration for CUSTOMER_A

Answer

CE1 is missing the network statement under router bgp 65001

Answer

The neighbor 10.0.0.2 is using an incorrect update-source

Question 9

An SP is implementing DiffServ at the edge router. Which TWO DSCP values are used for AF41 and AF31, respectively? (Choose two.)

Accepted Answer

DSCP 26. AF41 uses DSCP 34 (010001) and AF31 uses DSCP 26 (011010).

Answer

DSCP 10

Answer

DSCP 46

Answer

DSCP 18

Question 10

An SP is implementing traffic shaping on an MPLS PE-CE link. Which TWO statements are true about shaping compared to policing? (Select two.)

Accepted Answer

Policing can re-mark packets to a lower DSCP, shaping cannot.. Shaping buffers excess traffic to smooth bursts, while policing drops or re-marks excess packets. Shaping introduces delay due to buffering; policing can cause TCP retransmissions.

Answer

Policing typically introduces more delay than shaping.

Answer

Shaping is applied on ingress, policing on egress.

Answer

Both shaping and policing always result in packet loss.

Question 11

An SP is deploying SR-TE policies using PCEP. What is the role of the SR-PCE in this architecture?

Accepted Answer

It computes explicit paths and sends them to routers via PCEP. SR-PCE acts as a central controller that computes paths for SR-TE policies and communicates them via PCEP.

Answer

It forwards MPLS packets based on labels

Answer

It stores all routing tables in the network

Answer

It replaces the IGP for routing

Question 12

What is the primary difference between traffic shaping and policing in a QoS implementation?

Accepted Answer

Shaping buffers excess traffic, policing drops or re-marks. Shaping buffers excess traffic to smooth bursts, while policing drops or re-marks excess traffic to enforce a hard rate limit.

Answer

Shaping is applied at ingress, policing at egress

Answer

Shaping uses a token bucket, policing uses a leaky bucket

Answer

Shaping drops excess traffic, policing buffers it

Question 13

Which TWO methods can RESTCONF use to create a new data resource? (Choose two.)

Accepted Answer

POST. RESTCONF uses POST to create a new resource, and PUT can also create if the resource does not exist.

Answer

PATCH

Answer

DELETE

Answer

GET

Question 14

An SP is using MQC to configure QoS on a core router. Which TWO statements about MQC are correct? (Select two.)

Accepted Answer

A class-map can match multiple criteria using 'match-all' or 'match-any'.. MQC consists of class-map (classification), policy-map (define actions), and service-policy (apply). class-map uses match statements; policy-map can include bandwidth, priority, shape, etc.

Answer

A policy-map can be applied globally to all interfaces.

Answer

The 'service-policy' command is used in global configuration mode.

Answer

WRED can only be configured within a policy-map class.

Question 15

An SP is deploying SR-TE policies using a central controller. The controller needs to compute paths based on bandwidth and latency constraints. Which protocol is used between the controller and the routers to signal the SR-TE policies?

Accepted Answer

PCEP. PCEP (Path Computation Element Protocol) is used for communication between a PCE (controller) and PCC (router) to compute and instantiate SR-TE policies.

Answer

OSPF

Answer

BGP-LS

Answer

NETCONF

Question 16

Which THREE are valid reasons for using the 'ipv6 unicast-routing' command on a Cisco router?

Accepted Answer

It enables global IPv6 routing.. The 'ipv6 unicast-routing' command globally enables IPv6 unicast routing on the router, which is necessary for the router to forward IPv6 packets between interfaces. Without this command, the router will not process or forward IPv6 unicast traffic, even if IPv6 addresses are configured on interfaces.

Answer

It enables IPv6 on all interfaces.

Answer

It enables IPv6 multicast routing.

Question 17

In the context of SR-PCE, which protocol does the PCE use to communicate with the path computation client (PCC) to set up SR-TE policies?

Accepted Answer

PCEP. PCEP is the protocol used between PCE and PCC for path computation and setup.

Answer

NETCONF

Answer

OSPF

Answer

BGP-LS

Question 18

An SP network experiences congestion on a core link. The QoS policy uses CBWFQ with classes for voice (LLQ), video (bandwidth 30%), and data (bandwidth 50%). During congestion, voice traffic spikes to 25% of the link. What happens to video and data traffic?

Accepted Answer

Video and data share the remaining 75% as per their bandwidth percentages. LLQ is strict priority, so voice gets priority up to its police rate; if voice exceeds, it may be dropped. Video and data get their allocated bandwidths, but if voice exceeds its allowed priority, it may be policed, preventing starvation.

Answer

Video and data are dropped entirely until voice subsides

Answer

Video and data are unaffected

Answer

Video and data are treated as best effort

Question 19

Which RESTCONF HTTP method should be used to replace the entire configuration of a device interface?

Accepted Answer

PUT. RESTCONF uses PUT to replace a resource entirely; PATCH is for partial updates.

Answer

GET

Answer

DELETE

Answer

POST

Question 20

In the DiffServ model, which field is used in the IP header to mark packets for QoS treatment?

Accepted Answer

DSCP. The DiffServ model uses the 6-bit DSCP field in the IP header to classify packets.

Answer

IP Precedence

Answer

802.1p

Answer

MPLS EXP