350-501 Networking Practice Test 10 — 15 Questions

Question 1

A service provider is implementing 6VPE to provide IPv6 L3VPN services over an MPLS core. Which BGP address family must be configured on the PE routers to exchange IPv6 VPN routes?

Accepted Answer

VPNv6 unicast. 6VPE uses the VPNv6 address family (or IPv6 labeled unicast with VPN extensions) to carry IPv6 prefixes with VPN-IPv6 addresses.

Answer

IPv6 unicast

Answer

VPNv4 unicast

Answer

IPv4 unicast

Question 2

In BGP, which attribute is used to prevent routing loops when route reflectors are deployed?

Accepted Answer

Originator ID. Originator ID is used by route reflectors to prevent loops. If a router receives a route with its own router ID as originator, it discards it.

Answer

Cluster ID

Answer

AS_PATH

Answer

NEXT_HOP

Question 3

Which BGP attribute is locally significant and used to influence outbound traffic from an AS?

Accepted Answer

LOCAL_PREF. LOCAL_PREF is used to influence the path selection for outbound traffic within the AS, with higher preference preferred.

Answer

WEIGHT

Answer

AS_PATH

Answer

MED

Question 4

An SP is deploying IS-IS fast convergence using Partial Route Computation (PRC). Under which condition does PRC occur?

Accepted Answer

When a prefix is added or removed without topology change. PRC is triggered when a prefix changes but the topology remains unchanged. It recalculates only the affected prefixes, not the entire SPF tree.

Answer

When the IS-IS metric changes

Answer

When the system ID changes

Answer

When a new adjacency is formed

Question 5

A service provider is designing an OSPF network for both IPv4 and IPv6. Which two features are supported by OSPFv3 but not by OSPFv2? (Choose two.)

Accepted Answer

Support for IPv6. OSPFv3 runs over IPv6, supports multiple instances per link, and uses link-local addresses. OSPFv2 does not have these.

Answer

Virtual links

Answer

Authentication using MD5

Answer

Route redistribution

Question 6

Which three BGP attributes are considered in the route selection process before comparing MED? (Choose three.)

Accepted Answer

Weight. The order: weight, local pref, originate (locally originated), AS_PATH length, ORIGIN, MED. So weight, local pref, and AS_PATH length are before MED.

Answer

MED

Answer

Router ID

Question 7

An ISP is implementing 6PE for IPv6 transport over MPLS. Which two conditions are required for 6PE to work? (Choose two.)

Accepted Answer

BGP multiprotocol extensions for IPv6. 6PE requires BGP to carry IPv6 prefixes with an IPv4 next-hop (MPLS label), and the core MPLS network must support IPv4 LSPs.

Answer

IPv6 MPLS LSPs in the core

Answer

IPv6 next-hop in BGP updates

Answer

6PE requires 6VPE

Question 8

In IS-IS, which type of router is responsible for routing between different areas and also maintains a Level 1 Link State Database?

Accepted Answer

L1/L2 router. L1/L2 routers perform both intra-area and inter-area routing, maintaining both L1 and L2 LSDBs.

Answer

Level 2 router

Answer

Level 1 router

Answer

Area Border Router (ABR)

Question 9

An SP network engineer configures IS-IS with wide metrics. Which statement is true about IS-IS wide metrics compared to narrow metrics?

Accepted Answer

Wide metrics use Type-Length-Value (TLV) extensions to carry traffic engineering information.. Wide metrics use a 24-bit field, allowing values up to 16,777,215, and support TE extensions and segment routing.

Answer

Narrow metrics are required for IPv6 routing in IS-IS.

Answer

Wide metrics are only supported in Level 1 routing.

Answer

Narrow metrics support up to 63 cost values, while wide metrics support up to 255.

Question 10

A service provider uses OSPFv3 for IPv6 routing in the core. Which statement correctly describes OSPFv3 adjacency formation on a broadcast multiaccess network?

Accepted Answer

The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.. OSPFv3 operates similarly to OSPFv2 on broadcast networks, electing a DR and BDR using Hello protocol, and forming adjacencies with the DR.

Answer

OSPFv3 does not use DR/BDR election; instead, it forms full mesh adjacencies.

Answer

All routers on the network form full adjacencies with every other router.

Answer

The DR is elected based on the highest router ID, with a tiebreaker of highest interface priority.

Question 11

In BGP route selection, which attribute is considered before the MED when comparing routes from different ASes?

Accepted Answer

ORIGIN type. The BGP best path selection order is: weight, local pref, originated locally, AS_PATH length, ORIGIN, MED, etc. MED is considered after ORIGIN.

Answer

Local preference

Answer

Next-hop reachability

Answer

AS_PATH length

Question 12

A service provider wants to provide IPv6 connectivity over an MPLS IPv4 core using 6PE. Which BGP extension is required on the provider edge routers?

Accepted Answer

IPv6 address family with next-hop encoded as an IPv4-mapped IPv6 address. 6PE uses MP-BGP with the IPv6 address family and an IPv4 next-hop (the PE's IPv4 address), encoded via the IPv4-mapped IPv6 address format.

Answer

Labeled unicast IPv4 address family

Answer

VPNv4 address family with route-target extended community

Answer

IPv6 address family with next-hop encoded as an IPv6 address

Question 13

In IS-IS, what is the purpose of the Partial Route Computation (PRC)?

Accepted Answer

To recompute only the routes that are affected by a change in IP reachability. PRC recomputes only affected routes when a leaf changes, without full SPF, enabling faster convergence.

Answer

To compute the entire SPF tree after a topology change

Answer

To calculate the shortest path to all destinations in the L2 backbone

Answer

To repair IS-IS adjacency after link failure

Question 14

Which OSPF area type does not allow external routes (Type 5 LSAs) but does allow inter-area routes and can have a default route injected?

Accepted Answer

Stub area. A stub area blocks Type 5 LSAs, and a default route is injected for external destinations.

Answer

Totally stubby area

Answer

Backbone area (Area 0)

Answer

Not-So-Stubby Area (NSSA)

Question 15

A service provider deploys BGP route reflectors in the core. Which mechanism prevents routing loops within the route reflector cluster?

Accepted Answer

Originator-id attribute. The originator-id attribute is set by the route reflector to the router-id of the originating router, preventing loops by checking if the originator-id matches the local router-id.

Answer

Next-hop-self command

Answer

Cluster-list attribute and cluster-id

Answer

AS_PATH loop detection