300-410 Practice Test 13 — 15 Questions

Question 1

A network engineer runs the following command to troubleshoot a Route Summarization issue:

R1# debug eigrp packets
EIGRP: Sending HELLO on Serial0/0/0
  src 10.1.1.1, dst 224.0.0.10
EIGRP: Received UPDATE on Serial0/0/0 from 10.1.1.2
  src 10.1.1.2, dst 224.0.0.10
  update type: route
  prefix 10.0.0.0/16 metric 128576
EIGRP: Sending UPDATE on Serial0/0/0 to 10.1.1.2
  update type: summary
  prefix 10.0.0.0/16 metric 128576

What does this output indicate?

Accepted Answer

R1 is receiving and re-advertising the summary route 10.0.0.0/16, likely configured with a summary address.. The debug output shows EIGRP packet exchanges. R1 receives an UPDATE for prefix 10.0.0.0/16 and then sends an UPDATE with type 'summary' for the same prefix. This indicates that R1 is both learning and advertising a summary route.

Answer

R1 is only receiving the summary route and not advertising it.

Answer

The summary route is being suppressed due to a route filter.

Answer

The summary route is learned via OSPF and redistributed into EIGRP.

Question 2

An engineer configures EIGRP named mode on a router. A route is learned via EIGRP, but the router does not install it in the routing table. The show ip eigrp topology shows the route in passive state with a feasible distance. Which is the most likely explanation?

Accepted Answer

The router is configured as an EIGRP stub with 'receive-only', which prevents it from installing any EIGRP routes.. In named mode, EIGRP uses address-family configuration. The route may be learned but not installed if the 'no ip route-cache' or 'no ip routing' is misconfigured, or if the route is suppressed by a route-map. However, a common edge case is that the route is an internal route but the router is configured as a stub with 'receive-only', which prevents installing any routes.

Answer

The route is an external route and the EIGRP administrative distance is set to 255.

Answer

The 'metric weights' command is misconfigured, causing incorrect metric calculation.

Answer

The route is a summary route that is not advertised due to 'summary-address' configuration.

Question 3

A network engineer runs the following command to verify DHCPv6 guard policy:

R1# show ipv6 dhcp guard policy DHCP-POLICY

Policy: DHCP-POLICY
  Status: Active
  Device role: dhcp-client
  Trusted ports: none
  Untrusted ports: Fa0/0
  DHCPv6 guard: enabled
  DHCPv6 guard action: block
  DHCPv6 server validation: enabled
  DHCPv6 server list: 2001:db8::10

What does this output indicate?

Accepted Answer

The policy blocks DHCPv6 server messages on Fa0/0 except from server 2001:db8::10.. The output shows that DHCPv6 guard is enabled with an action of 'block' on untrusted port Fa0/0, and DHCPv6 server validation is enabled with a server list containing 2001:db8::10. This means the policy blocks DHCPv6 server messages (e.g., ADVERTISE, REPLY) received on Fa0/0, but allows them if they originate from the specified server address. Thus, only server messages from 2001:db8::10 are permitted, while all other DHCPv6 server messages are blocked.

Answer

The policy allows all DHCPv6 messages on Fa0/0 without any filtering.

Answer

The policy only applies to DHCPv6 client messages and ignores server messages.

Answer

The policy is inactive and not applied to any interface.

Question 4

A network engineer runs the following command on Router R1:

R1# show ip sla statistics 4

Round Trip Time (RTT) for Index 4
   Latest RTT: 300 ms
   Latest RTT (milliseconds): 300
   Latest RTT (microseconds): 300000
   Number of successes: 45
   Number of failures: 55
   Operation time to live: Forever
   Output: Over threshold

R1# show track 2
Track 2
  IP SLA 4 reachability
  Reachability is Down
    5 changes, last change 00:00:05
  Latest operation return code: Over threshold
  Latest RTT (milliseconds): 300
  Tracked by:
    ip route 0.0.0.0 0.0.0.0 192.168.2.1 track 2

Based on this output, which statement is correct?

Accepted Answer

The IP SLA threshold has been exceeded, causing the track to go down and the static route to be removed.. The track shows 'Down' because the IP SLA return code is 'Over threshold'. This means the threshold was exceeded, and the track has brought down the static route. The failures (55) are high, but the key is that the track is down due to the threshold violation.

Answer

The IP SLA operation is failing because the target is unreachable.

Answer

The tracked static route is active because the IP SLA has successes.

Answer

The IP SLA operation has a 55% failure rate, but the track is still up.

Question 5

R1 and R2 are iBGP peers in AS 65001. R1 has: neighbor 10.1.1.2 route-reflector-client. R2 advertises a prefix 10.0.0.0/8 with a community of no-export. R1 reflects this prefix to its other client R3. R3 is in a different AS (65002) via eBGP. R3 receives the prefix but does not advertise it to its eBGP neighbor R4 in AS 65003. What is the root cause?

Accepted Answer

The no-export community on the prefix prevents R3 from advertising it to eBGP neighbor R4.. The community no-export attached to the prefix prevents it from being advertised to any eBGP peers. When R1 reflects the prefix to R3 (iBGP), the community is preserved. R3, upon advertising to R4 (eBGP), checks the community and withholds the advertisement because of the no-export community. The root cause is that the no-export community is present on the prefix, which blocks eBGP advertisement.

Answer

R1 should have stripped the community before reflecting to R3.

Answer

R3 is missing the send-community command to its eBGP neighbor.

Answer

The route-reflector-client command on R1 should be on R2 instead.

Question 6

Which IPv6 traffic filter can be used to match traffic based on the Flow Label field?

Accepted Answer

IPv6 access-list with the 'flow-label' option. The IPv6 access-list supports the 'flow-label' keyword, which allows matching packets based on the 20-bit Flow Label field in the IPv6 header. This field is defined in RFC 2460 and is used for per-flow processing, such as QoS or load balancing, without needing to inspect upper-layer headers.

Answer

IPv6 prefix-list

Answer

IPv6 route-map with match ipv6 address

Answer

IPv6 uRPF

Question 7

A network engineer redistributes OSPF routes into EIGRP on Router R1. After redistribution, Router R3, which is an EIGRP neighbor of R1, starts experiencing routing loops for the 192.168.1.0/24 network. R1 configuration: router eigrp 100, redistribute ospf 1 metric 10000 100 255 1 1500, route-map RM-OSPF-to-EIGRP. The route-map sets tag 100. R3 shows: 'show ip route 192.168.1.0' points to R1, but traceroute shows packets looping between R1 and R3. What is the root cause?

Accepted Answer

The redistribution metric is too low, causing the route to be preferred over the OSPF path, but the loop is due to missing route tagging and filtering on redistribution.. The root cause is that the redistributed OSPF routes into EIGRP lack proper route tagging and filtering, causing R3 to re-advertise the 192.168.1.0/24 route back to R1, creating a routing loop. The route-map sets a tag of 100, but without an inbound filter on R1 (e.g., a distribute-list or route-map denying tagged routes), R1 will accept the route from R3, leading to a loop. Option A correctly identifies that the metric is sufficient for the route to be preferred, but the missing loop-prevention mechanism is the core issue.

Answer

The EIGRP metric values are incorrect; the delay value of 100 is too high, causing the route to be considered unreachable.

Answer

The route-map is applied in the wrong direction; it should be applied to the redistribute command under OSPF instead of EIGRP.

Answer

R3 has a static route for 192.168.1.0/24 pointing to R1, overriding the dynamic route.

Question 8

A dual-stack network uses BGP for IPv6 between two ISPs. R1 (AS 100) receives a full BGP table from R2 (AS 200). R1 has an IPv6 ACL applied inbound on the interface to R2 that permits only BGP (TCP 179) and denies all other traffic. R1 also has uRPF configured in strict mode on the same interface. R1's BGP table has a route to 2001:db8:1::/48 with next-hop 2001:db8:2::2. R1's routing table shows the route, but traffic from R1 to 2001:db8:1::1 fails. R1 shows 'show ipv6 cef 2001:db8:1::/48' points to 2001:db8:2::2 via the interface to R2. What is the root cause?

Accepted Answer

The ACL on R1 blocks the return traffic from the destination, which is not BGP, causing the ping to fail.. The IPv6 ACL on R1 permits only BGP (TCP port 179) inbound from R2. When R1 sends a ping to 2001:db8:1::1, the return ICMPv6 echo-reply traffic from the destination (via R2) is not BGP and is therefore denied by the inbound ACL, causing the ping to fail. The BGP table and routing table are correct, but the ACL blocks the non-BGP return traffic.

Answer

uRPF strict mode drops the outgoing traffic because the source address is not reachable via the interface.

Answer

The next-hop 2001:db8:2::2 is not reachable due to a missing ND entry.

Answer

BGP next-hop resolution fails because the next-hop is not in the FIB.

Question 9

Drag and drop the steps to verify and validate Device Management operational state into the correct order, from first to last.

Accepted Answer

Check management interface status with show ip interface brief. Start by checking the management interface status, then confirm the management protocol is operational, verify the device is reachable, validate data model support, and finally perform a test retrieval of configuration data.

Question 10

In OSPF, what is the default behavior for auto-summary on Cisco IOS-XE?

Accepted Answer

Auto-summary is disabled by default. Cisco IOS-XE has auto-summary disabled by default for OSPF, meaning that redistributed routes are not summarized to their classful boundaries unless explicitly configured.

Answer

Auto-summary is enabled by default

Answer

Auto-summary is only enabled for external routes

Answer

Auto-summary is enabled only for inter-area routes

Question 11

Which LDP message type is used to request label bindings from a neighbor?

Accepted Answer

Label Request message. The Label Request message is sent by an LDP router to request a label binding for a specific FEC from its neighbor.

Answer

Label Mapping message

Answer

Label Withdraw message

Answer

Label Release message

Question 12

An engineer is troubleshooting a network where R1 and R2 are running EIGRP, and R2 redistributes a static route for 192.168.1.0/24 into EIGRP. R1 also learns the same prefix via OSPF from R3 with an AD of 110. The engineer observes that R1 prefers the EIGRP external route (AD 170) over the OSPF route. What configuration change would cause this behavior?

Accepted Answer

The engineer applied the distance eigrp 90 100 command under EIGRP, lowering the AD for external routes to 100.. By default, EIGRP external routes have an AD of 170, and OSPF has AD 110, so OSPF should be preferred. If the EIGRP external route is preferred, the AD must have been lowered, likely via the distance command under EIGRP.

Answer

The OSPF route is a type 5 LSA, which has a higher AD than type 3 LSAs.

Answer

The OSPF route has a metric of 20, while the EIGRP route has a metric of 2560.

Answer

The static route was redistributed with a route-map that sets the EIGRP metric to 1.

Question 13

A network engineer is troubleshooting an issue where IPv6 hosts are receiving multiple Router Advertisements from different routers, causing routing instability. The switch is configured with IPv6 First Hop Security features. The engineer wants to ensure that only the primary router's RAs are accepted by hosts. What is the most effective solution?

Accepted Answer

Configure RA Guard with a policy that includes the primary router's MAC address in the allowed list and apply it to all ports.. RA Guard with a policy that includes the primary router's MAC address in the allowed list is the most effective solution because it filters Router Advertisements (RAs) at Layer 2, permitting only RAs from the trusted primary router. This directly addresses the issue of multiple RAs causing routing instability by blocking RAs from any other source, such as the secondary router, without affecting other IPv6 traffic. RA Guard is an IPv6 First Hop Security feature designed specifically to prevent rogue or unwanted RAs from being processed by hosts.

Answer

Enable DHCPv6 Guard to block DHCPv6 messages from the secondary router.

Answer

Use IPv6 Source Guard to filter traffic from the secondary router.

Answer

Configure the switch to act as a router and send its own RAs with a higher priority to override the secondary router.

Question 14

Which TWO statements about IPv6 unicast RPF (uRPF) behavior in Cisco IOS-XE are correct? (Choose TWO.)

Accepted Answer

Strict mode uRPF drops packets if the source address is not reachable via the incoming interface.. IPv6 unicast RPF strict mode verifies that the source address of an incoming packet is reachable via the exact interface on which the packet arrived, according to the FIB. If the source address is not reachable through that interface, the packet is dropped. This prevents spoofed traffic from entering the network from an unexpected path.

Answer

The default uRPF mode on Cisco IOS-XE is strict mode.

Answer

IPv6 uRPF can be applied globally using the 'ipv6 unicast-rpf' command.

Answer

uRPF checks both source and destination addresses in the IPv6 header.

Question 15

A network engineer is troubleshooting a route redistribution issue between two EIGRP processes. Router R1 runs EIGRP AS 100 and EIGRP AS 200, and redistributes routes between them. The engineer notices that routes from EIGRP AS 100 are not appearing in the EIGRP topology table of AS 200 on R1. The redistribute eigrp 100 command is configured under EIGRP AS 200. What is the most likely cause?

Accepted Answer

The redistribute eigrp 100 command under EIGRP AS 200 is missing the metric specification.. When redistributing between EIGRP processes, the redistribute command must include the metric values (bandwidth, delay, reliability, load, MTU) or a default-metric must be configured. Without a metric, the redistributed routes are not accepted.

Answer

EIGRP AS 100 has a higher administrative distance than EIGRP AS 200.

Answer

The redistribute eigrp 100 command under EIGRP AS 200 is missing the subnets keyword.

Answer

EIGRP AS 200 has a route map that is filtering all routes.