300-410 Practice Test 18 — 15 Questions

Question 1

A network engineer runs the following command to troubleshoot OSPF route redistribution:

R1# show ip ospf database external 5.5.5.5

OSPF Router with ID (1.1.1.1) (Process ID 1)

Type-5 AS External Link States

LS age: 120
  Options: (No TOS-capability, DC, Upward)
  LS Type: AS External Link
  Link State ID: 5.5.5.5 (External Network Number)
  Advertising Router: 3.3.3.3
  LS Seq Number: 80000001
  Checksum: 0xABCD
  Length: 36
  Network Mask: /32
    Metric Type: 2 (Larger than any link state path)
    TOS: 0
    Metric: 20
    Forward Address: 0.0.0.0
    External Route Tag: 0

What does this output indicate?

Accepted Answer

The route was redistributed into OSPF by router 3.3.3.3 with a metric of 20.. The output shows an OSPF Type 5 External LSA for prefix 5.5.5.5/32, advertised by router 3.3.3.3 with a metric type E2 and metric 20.

Answer

The prefix 5.5.5.5/32 is a network inside the OSPF domain.

Answer

The forward address indicates the next-hop is 5.5.5.5.

Answer

This is a Type 4 Summary ASBR LSA.

Question 2

Which OSPF LSA type is flooded only within the originating area and is used for loop prevention by describing the topology of the area?

Accepted Answer

Type 1 LSA (Router LSA). Type 1 Router LSAs describe the router's links and are flooded only within the area. They provide topology information for loop prevention within the area.

Answer

Type 2 LSA (Network LSA)

Answer

Type 3 LSA (Summary LSA)

Answer

Type 4 LSA (ASBR Summary LSA)

Question 3

A large enterprise network is experiencing intermittent reachability between VRF-A on Router R1 and VRF-B on Router R2. R1 has the following relevant configuration: ip vrf VRF-A, rd 100:1, route-target export 100:1, route-target import 100:2. R2 shows: ip vrf VRF-B, rd 200:2, route-target export 200:2, route-target import 200:1. The link between R1 and R2 is configured with VRF forwarding VRF-A on R1 and VRF forwarding VRF-B on R2. What is the root cause?

Accepted Answer

The route-target import and export values are mismatched between the VRFs, preventing route exchange.. The route-target import/export values are mismatched for the VRF-Lite scenario. In VRF-Lite, route-targets are used for route leaking, but on a direct link, the VRFs must match or route leaking must be configured properly. Here, R1 imports routes with RT 100:2, which R2 exports as 200:2, not 100:2. R2 imports RT 200:1, but R1 exports 100:1. Thus, no routes are exchanged, causing unreachability.

Answer

The RD values must match for VRF-Lite to work on a direct link.

Answer

The VRFs must have the same name on both routers for direct connectivity.

Answer

The interface must be in the same VRF on both ends; route-targets are irrelevant for VRF-Lite.

Question 4

An engineer configures CoPP on a router that is a route reflector for iBGP. The policy includes a class-map matching BGP traffic and polices it to 500 pps. After deployment, some iBGP prefixes are missing from the route reflector's table, but the BGP sessions are up. Which is the most likely explanation?

Accepted Answer

CoPP drops BGP update packets from specific clients due to rate limiting, so those prefixes are not learned.. B is correct because CoPP polices BGP traffic to 500 pps, and if BGP update packets from specific iBGP clients exceed this rate, they are dropped. Since BGP keepalives are small and infrequent, the session remains up, but the dropped updates prevent the route reflector from learning certain prefixes, leading to missing routes in the table.

Answer

CoPP drops BGP keepalive packets, causing the session to reset.

Answer

The route reflector is configured to ignore certain prefixes.

Answer

CoPP only affects eBGP, not iBGP.

Question 5

Which TWO statements correctly describe the behavior of OSPFv3 when troubleshooting neighbor adjacency issues on a Cisco IOS-XE router? (Choose TWO.)

Accepted Answer

OSPFv3 neighbor adjacencies are formed using the link-local IPv6 address of the neighbor.. OSPFv3 uses link-local addresses for neighbor adjacency formation and relies on IPv6 link-local addresses for next-hop resolution. The router ID is still a 32-bit value, and the network type must be configured under the interface. The 'ipv6 ospf' command is used to enable OSPFv3 on an interface, not 'ipv6 router ospf'.

Answer

The OSPFv3 router ID is a 128-bit value derived from the highest loopback IPv6 address.

Answer

The 'ipv6 router ospf' command is used to enable OSPFv3 on an interface.

Answer

OSPFv3 uses the network type configured under the OSPFv3 process globally, not per interface.

Question 6

Which statement correctly describes the behavior of the 'logging synchronous' command on a Cisco IOS device?

Accepted Answer

It causes syslog messages to be displayed only after a carriage return.. The 'logging synchronous' command prevents syslog messages from interrupting console command output by buffering them until the user finishes typing.

Answer

It disables all syslog messages on the console line.

Answer

It changes the severity level of messages sent to the console.

Answer

It enables logging to a synchronous serial interface.

Question 7

Which syslog severity level is used for informational messages that are not errors but may be useful for monitoring?

Accepted Answer

Severity 6 (Informational). Severity 6 is defined as 'Informational' in RFC 5424, used for non-error messages.

Answer

Severity 5 (Notice)

Answer

Severity 7 (Debug)

Answer

Severity 0 (Emergency)

Question 8

What is the default port number used by syslog servers to receive UDP syslog messages?

Accepted Answer

UDP 514. RFC 5424 specifies UDP port 514 as the default for syslog messages.

Answer

UDP 162

Answer

TCP 514

Answer

UDP 161

Question 9

Drag and drop the steps to troubleshoot syslog connectivity failures into the correct order, from first to last.

Accepted Answer

Ping syslog server from router. First, verify reachability to the syslog server using ping. Then, check if the syslog server port (UDP 514) is open. Next, review the logging configuration on the router. After that, examine ACLs that may block syslog traffic. Finally, enable debug ip udp to monitor syslog packet flow.

Question 10

An engineer configures OSPFv3 with multiple areas. On the ABR, routes from area 1 are not being advertised into area 0. Which is the most likely explanation?

Accepted Answer

The ABR does not have a direct interface in area 0.. OSPFv3 requires that the ABR have a direct connection to area 0. If the ABR is not directly connected to area 0, it will not advertise inter-area routes. Additionally, OSPFv3 uses the same rule as OSPFv2: an ABR must have at least one interface in area 0 to function as an ABR.

Answer

The ABR has a higher router ID than the other routers.

Answer

The OSPFv3 process is configured with the 'no-redistribution' command.

Answer

The ABR is configured as a stub router.

Question 11

A network engineer runs the following command to troubleshoot a Device Access Control issue:

R1# show ip bgp vpnv4 vrf CUSTOMER-A 10.10.10.0/24

BGP routing table entry for 10.10.10.0/24, version 2
Paths: (1 available, best #1, table CUSTOMER-A)
  Not advertised to any peer
  Refresh Epoch 1
  Local
    10.1.1.2 from 10.1.1.2 (10.1.1.2)
      Origin IGP, metric 0, localpref 100, valid, internal, best
      Extended Community: RT:100:100
      mpls labels in/out nolabel/101

What does this output indicate?

Accepted Answer

The route 10.10.10.0/24 is installed in VRF CUSTOMER-A with an MPLS label of 101 for forwarding.. The output shows that the route 10.10.10.0/24 is installed in VRF CUSTOMER-A (table CUSTOMER-A) with an MPLS label of 101 for outgoing forwarding, as indicated by 'mpls labels in/out nolabel/101'. The route is valid, internal, and best, meaning it is used for forwarding despite not being advertised to any peer. This confirms that the MPLS label is applied for forwarding within the VRF context.

Answer

The route 10.10.10.0/24 is not installed because it is not advertised to any peer.

Answer

The route 10.10.10.0/24 is learned from an external BGP peer.

Answer

The route 10.10.10.0/24 has no MPLS label and will be forwarded using IP lookup.

Question 12

A network engineer is troubleshooting a manual IPv6-in-IPv4 tunnel between two Cisco routers. The tunnel is up, and both routers can ping each other's tunnel IPv6 addresses. However, traffic from a host behind Router A to a host behind Router B fails. The engineer notices that Router A has a route to the remote IPv6 prefix via the tunnel, but Router B does not have a route to the local IPv6 prefix. What is the most likely cause?

Accepted Answer

Router B is missing a static route pointing the local IPv6 prefix to the tunnel interface.. The tunnel is up and both routers can ping each other's tunnel IPv6 addresses, confirming that the tunnel itself is operational. However, traffic from a host behind Router A to a host behind Router B fails because Router B lacks a route back to the local IPv6 prefix (the network behind Router A). For bidirectional communication, both routers must have a route to the remote IPv6 prefix pointing to the tunnel interface. Since Router B is missing this static route, it cannot forward return traffic into the tunnel, causing the failure.

Answer

The tunnel mode is set to 'ipv6ip 6to4' instead of 'ipv6ip'.

Answer

The tunnel source on Router B is misconfigured with the wrong IPv4 address.

Answer

The IPv6 access-list on Router B is blocking incoming traffic from the local prefix.

Question 13

A network engineer is troubleshooting an intermittent BGP session failure between two routers. The BGP session drops every few hours and recovers after a few seconds. The engineer checks the logs and sees that an EEM applet is triggered just before each failure. The applet is configured to run a script that clears the BGP session when a specific syslog message is generated. What is the most likely cause of the BGP session failure?

Accepted Answer

The EEM applet is clearing the BGP session as part of its configured action.. The EEM applet is the root cause because it is configured to clear the BGP session upon a specific syslog event. The engineer should review the applet's trigger condition and action to identify why it is being triggered incorrectly or unnecessarily.

Answer

The BGP session is failing due to a physical layer issue.

Answer

The BGP session is failing due to a routing loop.

Answer

The EEM applet is causing a memory leak that crashes the BGP process.

Question 14

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 10.1.1.0/24
BGP routing table entry for 10.1.1.0/24, version 2
Paths: (1 available, best #1, table default)
  Advertised to update-groups:
     1
  Refresh Epoch 1
  Local
    10.1.1.1 from 0.0.0.0 (10.1.1.1)
      Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, best
      rx pathid: 0, tx pathid: 0x0

Based on this output, which statement is correct?

Accepted Answer

The route 10.1.1.0/24 is locally originated and is the best path.. The output shows a locally originated network (10.1.1.0/24) with next hop 10.1.1.1 (the router itself). It is marked as valid, sourced, and best, meaning it is injected into BGP and will be advertised to peers.

Answer

The route 10.1.1.0/24 was learned from an eBGP peer.

Answer

The route 10.1.1.0/24 has a weight of 100.

Answer

The route 10.1.1.0/24 is not being advertised to any peer.

Question 15

A network engineer runs the following command on Router R1:

R1# show bgp ipv4 unicast 10.4.4.0/24
BGP routing table entry for 10.4.4.0/24, version 8
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  Refresh Epoch 1
  65006
    10.1.16.6 from 10.1.16.6 (10.6.6.6)
      Origin IGP, metric 0, localpref 100, valid, external, best
      rx pathid: 0, tx pathid: 0x0

Based on this output, what is the most likely reason the route is not advertised to any peer?

Accepted Answer

There is an outbound route-map or prefix-list filtering the route.. The route is valid and best, but not advertised. This could be due to outbound filtering (route-map, prefix-list) applied to the BGP neighbor, or the neighbor might not be configured to receive this prefix. Another possibility is that the route is suppressed by a policy.

Answer

The route has a local preference of 100, which is too low.

Answer

The BGP session to the neighbor is down.

Answer

The route is not in the routing table.