350-501 Practice Test 34 — 15 Questions

Question 1

A service provider is designing a BGP-based network. Which TWO are characteristics of BGP within a service provider core?

Accepted Answer

IBGP sessions require a full mesh or route reflectors to avoid routing loops. Option A is correct because iBGP requires that all routers within the same AS form a full mesh of sessions, or use route reflectors (or confederations) to relax that requirement, since routes learned via iBGP are not re-advertised to other iBGP peers by default, which prevents loops but demands a full mesh or route reflectors. Option E is correct because BGP itself does not provide next-hop reachability; the next-hop IP address carried in BGP updates must be resolvable via the IGP (OSPF, IS-IS, etc.) running inside the AS, so the IGP is essential for BGP to function within the service provider core. Option B is incorrect because the MED attribute is optional and non-transitive, not mandatory for all routes. Option C is incorrect because AS path loop prevention applies to eBGP; within iBGP, the AS path is not used for loop prevention since all routers share the same AS number. Option D is incorrect because route reflectors do not modify the AS path; they use the ORIGINATOR_ID and CLUSTER_LIST attributes to prevent loops.

Answer

BGP MED attribute is mandatory for all routes

Answer

BGP uses the AS path for loop prevention in iBGP

Answer

BGP route reflectors always modify the AS path

Question 2

In an MPLS L3VPN, how can a service provider prevent a CE device from learning the MPLS label stack and potentially spoofing labels?

Accepted Answer

Disable MPLS on the PE-CE interface. Disabling MPLS on the PE-CE interface prevents the CE from receiving or sending labeled packets, so the CE never sees the MPLS label stack and cannot spoof labels into the provider core. The PE still runs MPLS on its core-facing interfaces and performs label imposition/ disposition at the edge, keeping the label domain entirely within the provider network. This is the standard security practice for untrusted CE devices.

Answer

Use LDP authentication between PE and CE

Answer

Configure MPLS VPN route-target filtering

Answer

Enable TTL propagation on the PE-CE link

Question 3

Drag and drop the steps for the BGP route selection process (best path selection) in order.

Accepted Answer

Weight, then Local Preference, then Locally Originated, then AS_PATH Length, then MED. BGP best path selection follows a specific order: weight, local preference, locally originated, AS_PATH length, MED.

Answer

Local Preference, then Weight, then Locally Originated, then AS_PATH Length, then MED

Answer

Weight, then Local Preference, then AS_PATH Length, then MED, then Locally Originated

Answer

Weight, then AS_PATH Length, then Local Preference, then Locally Originated, then MED

Question 4

An engineer configures the 'set-overload-bit' command on an IS-IS router. What is the immediate effect on the network?

Accepted Answer

The router is not used as a transit path but still has routes.. The 'set-overload-bit' command causes the IS-IS router to set the overload bit in its Link State PDUs (LSPs). This signals to other routers that the advertising router should not be used for transit traffic, but it still participates in SPF calculations and can be reached as a leaf or end node. Therefore, the router retains its routes and adjacency, but other routers will not forward traffic through it.

Answer

The router stops participating in SPF calculations.

Answer

The router's LSPs are no longer advertised.

Answer

The router's neighbors drop adjacency.

Question 5

A network operator deploys a QoS policy on a route reflector to classify traffic based on BGP community values. However, the policy is not matching the intended traffic. Which is the most likely cause?

Accepted Answer

The class-map uses a match statement referencing BGP community values, which are not visible at the QoS classification stage.. BGP community values are exchanged as part of the BGP routing update and are stored in the BGP table, but they are not carried in the IP packet header. QoS classification in Cisco IOS operates on fields within the Layer 2 or Layer 3 packet header (e.g., DSCP, IP precedence, CoS) and cannot inspect BGP attributes like community values. Therefore, a class-map using a match statement for BGP communities will never match traffic at the QoS classification stage, making this the most likely cause of the policy not working.

Answer

The policy-map is applied to the wrong interface.

Answer

The service-policy is applied in the wrong direction (input vs output).

Answer

The class-default class is consuming all traffic.

Question 6

A service provider uses BGP FlowSpec (RFC 8955) to mitigate DDoS attacks. Which component in the network is responsible for originating the FlowSpec rules and distributing them to routers?

Accepted Answer

A FlowSpec controller (e.g., router with policy or SDN controller). BGP FlowSpec rules are originated by a FlowSpec controller—either a router configured with flow-spec policy or an SDN/centralized controller—which encodes match conditions (e.g., source/dest IP, ports, protocols) and actions (drop, rate-limit, redirect) into BGP FlowSpec NLRI. The controller then distributes these rules via iBGP/eBGP to routers across the network, which install them as flow-based filters. This separation of detection/orchestration from enforcement is the standard architecture in RFC 8955 deployments.

Answer

The trigger router used for RTBH

Answer

The victim's CE router

Answer

An anomaly detection system like Cisco Peakflow

Question 7

An engineer is configuring BGP route reflectors to scale iBGP. Which TWO attributes are used to prevent routing loops in a route reflector cluster? (Choose two.)

Accepted Answer

ORIGINATOR_ID. CLUSTER_LIST and ORIGINATOR_ID are used to prevent loops. CLUSTER_LIST is a sequence of cluster IDs; ORIGINATOR_ID identifies the originator.

Answer

NEXT_HOP

Answer

LOCAL_PREF

Answer

AS_PATH

Question 8

Which QoS mechanism marks packets at the edge of the network to classify traffic into different service classes?

Accepted Answer

Marking. Marking is the QoS mechanism that sets the Differentiated Services Code Point (DSCP) or IP Precedence bits in the packet header at the ingress edge of the network. This classification allows downstream devices to apply per-hop behaviors (PHBs) based on the marked value, as defined in RFC 2474 and RFC 2597. Unlike queuing, shaping, or policing, marking does not delay or drop packets; it only modifies the packet header to indicate the desired service class.

Answer

Queuing

Answer

Shaping

Answer

Policing

Question 9

In Segment Routing over IPv6 (SRv6), what is the function of the SRH (Segment Routing Header)?

Accepted Answer

It contains the segment list (ordered list of SIDs). The Segment Routing Header (SRH) is a new IPv6 extension header defined in RFC 8754 that carries an ordered list of Segment Identifiers (SIDs). When a packet is forwarded along a segment-routed path, the SRH encodes the explicit path by listing each segment (node or adjacency SID) in sequence, and the active segment is updated as the packet traverses each hop. This allows the source node to steer packets through a specific path without intermediate nodes needing to maintain per-flow state.

Answer

It replaces the IPv6 header to reduce overhead

Answer

It provides OAM capabilities for path monitoring

Answer

It uses the IPv6 flow label to encode the path

Question 10

When deploying IS-IS in a large service provider core, what is the recommended network type on Ethernet interfaces to improve scalability?

Accepted Answer

point-to-point. In a large service provider core, configuring IS-IS interfaces as point-to-point (network type point-to-point) improves scalability by eliminating the need for Designated Router (DIS) election and the associated pseudonode LSPs. This reduces the number of LSPs in the link-state database, lowers CPU and memory overhead, and speeds up convergence, which is critical in dense core networks.

Answer

loopback

Answer

point-to-multipoint

Answer

non-broadcast

Answer

broadcast

Question 11

Which THREE YANG data nodes are part of the Cisco-IOS-XR-qos-ma-cfg module for defining a QoS policy-map? (Choose three.)

Accepted Answer

class. The 'class' YANG data node is defined in the Cisco-IOS-XR-qos-ma-cfg module to specify a traffic class within a QoS policy-map. This node allows you to associate a class-map with the policy, enabling differentiated treatment of traffic based on classification criteria.

Answer

urn:cisco:params:xml:ns:yang:Cisco-IOS-XR-qos-ma-cfg

Answer

interface

Question 12

Refer to the exhibit. Which statement is correct about the LDP bindings for prefix 10.0.0.0/24?

Accepted Answer

There are two remote label bindings for this prefix from different LSRs.. The exhibit shows two remote label bindings for prefix 10.0.0.0/24, one with an incoming label of 18 from LSR 192.168.1.2 and another with an incoming label of 19 from LSR 192.168.1.3. This indicates that two different LSRs have advertised label bindings for the same prefix, which is typical in an MPLS network with multiple paths. Therefore, option A is correct.

Answer

Both remote bindings are from the same LSR.

Answer

The local label for this prefix is 18.

Answer

The router is performing PHP for this prefix.

Question 13

Which THREE steps are required when configuring MPLS L3VPN on a PE router? (Choose three.)

Accepted Answer

Create a VRF definition. Option B is correct because a VRF definition is the foundational step on a PE router: it creates the separate routing/forwarding table that isolates each customer's VPN routes and is referenced by the RD and route-targets. Option C is correct because the PE must configure the BGP address-family ipv4 vrf (per-VRF address family) to exchange the customer's IPv4 VPN routes with CE routers or other PEs, carrying the VPNv4 reachability. Option E is correct because the customer-facing interface must be assigned to the VRF (e.g., ip vrf forwarding <name>) so that received packets are placed into the correct VRF table and the interface participates in that VPN. Option A is not required because BGP on the CE is a customer-side routing choice, not a mandatory PE configuration step for MPLS L3VPN. Option D is not required because route-target import/export is configured directly under the VRF (route-target export/import), not via a route-map, so the stated method is incorrect.

Answer

Configure BGP on the CE router to advertise routes to PE

Answer

Configure route-target import/export using route-map

Question 14

An SP is managing a large MPLS network and needs to verify the MPLS forwarding entries for a specific VRF. Which command provides the most complete information for the VRF?

Accepted Answer

show mpls forwarding-table vrf . The 'show mpls forwarding-table vrf ' command displays the complete MPLS forwarding entries for a specific VRF, including the incoming label, outgoing label, next-hop, and outgoing interface. This command is specifically designed to verify MPLS label-switched paths (LSPs) for a VRF, which is essential for troubleshooting MPLS VPN forwarding. It provides the most complete information for MPLS forwarding, as it shows both the label operations (swap, pop, push) and the VRF-specific forwarding details.

Answer

show ip cef vrf <name>

Answer

show mpls vrf <name>

Answer

show bgp vpnv4 unicast all labels

Question 15

A service provider is deploying OSPFv3 for IPv6 in its core. The network uses multiple areas. Which LSA type is used by OSPFv3 to advertise prefix information for inter-area routes?

Accepted Answer

Inter-Area Prefix LSA (Type 0x2003). In OSPFv3, the Inter-Area Prefix LSA (Type 0x2003) is used to advertise IPv6 prefix information for inter-area routes. It is generated by Area Border Routers (ABRs) to describe networks in other areas, replacing the functionality of Type 3 summary LSAs in OSPFv2 but with explicit prefix information.

Answer

Network LSA (Type 0x2002)

Answer

Intra-Area Prefix LSA (Type 0x2009)

Answer

Router LSA (Type 0x2001)