300-410 Mock Exam 76 — 25 Questions

Question 1

A network engineer configures IP SLA to track a BGP next-hop for a backup path. Router R1 has:

ip sla 7
 icmp-echo 192.168.3.3 source-ip 10.0.0.1
 frequency 5
ip sla schedule 7 life forever start-time now

track 7 ip sla 7 reachability

router bgp 65001
 neighbor 192.168.3.3 remote-as 65003
 neighbor 192.168.3.3 fall-over bfd
 neighbor 192.168.3.3 track 7

But when the link to 192.168.3.3 goes down, the BGP session resets after 5 seconds, but the backup route is not used immediately. What is the root cause?

Accepted Answer

The BGP fall-over bfd overrides the track, so the BGP session resets via BFD, but the track remains up, preventing the backup route from being installed.. The BGP fall-over bfd and track 7 are both configured. When the link goes down, BFD detects the failure quickly and resets the BGP session. However, the track 7 might still be up because the IP SLA probe might be successful via an alternate path, so the tracked route is not removed. The correct answer is that the track 7 is not used because BFD takes precedence, and the track does not influence the route removal.

Answer

The IP SLA frequency is too low, so the track does not detect the failure quickly enough.

Answer

The backup route has a higher administrative distance, so it is not installed until the primary route is removed, but the primary route is still present.

Answer

The track 7 is not applied to the BGP neighbor correctly; it should be under the address-family.

Question 2

Which TWO commands can be used to verify the administrative distance of a route in a Cisco IOS router? (Choose TWO.)

Accepted Answer

show ip route. The show ip route command displays the routing table including the administrative distance for each route. The show ip protocols command displays routing protocol parameters including the default and any configured administrative distances. The other options either do not show administrative distance or are incorrect commands.

Answer

show ip interface brief

Answer

show running-config | include distance

Answer

show ip ospf interface

Question 3

Which TWO configuration steps are required to change the administrative distance for routes learned from a specific neighbor in EIGRP? (Choose TWO.)

Accepted Answer

Configure a prefix list to match the routes from the neighbor.. To change the AD for routes from a specific EIGRP neighbor, you must first configure a prefix list to match the routes, then apply it using the distance command in EIGRP router configuration mode. The distance command can specify a different AD for routes matching a prefix list from a specific neighbor.

Answer

Use the distance eigrp command in router configuration mode.

Answer

Configure an access list to permit the routes from the neighbor.

Answer

Use the redistribute command to change the administrative distance.

Question 4

A large enterprise uses IP SLA to track a route to a remote site via an MPLS L3VPN. Router R1 (PE) has:

ip sla 8
 icmp-echo 10.10.10.10 source-ip 192.168.1.1
 frequency 10
ip sla schedule 8 life forever start-time now

track 8 ip sla 8 reachability

ip route vrf CUSTOMER 10.10.10.0 255.255.255.0 192.168.1.2 track 8

The MPLS network is operational, but the route is intermittently removed. Show output on R1:

show ip route vrf CUSTOMER 10.10.10.0
Routing entry for 10.10.10.0/24
  Known via "static", distance 1, metric 0
  Last update from 192.168.1.2 on GigabitEthernet0/0
  * 192.168.1.2, via GigabitEthernet0/0

But the track is down:

show track 8
Track 8
  IP SLA 8 reachability
  Reachability is Down
  3 changes, last change 00:00:15

What is the root cause?

Accepted Answer

The IP SLA is not configured with the vrf CUSTOMER keyword, so the probe is sent in the global table and cannot reach the target in the VRF.. The IP SLA probe is sent to 10.10.10.10, but the source IP is 192.168.1.1. In an MPLS L3VPN, the VRF CUSTOMER might have a different routing table. The probe is sent in the global table unless configured with vrf. The correct answer is that the IP SLA is not VRF-aware, so the probe fails, but the static route is still installed because the track is down but the route is not removed immediately due to the delay or because the route is still in the table from a previous state.

Answer

The MPLS label distribution is failing, causing the IP SLA probe to be dropped.

Answer

The source IP 192.168.1.1 is not in the VRF CUSTOMER, so the probe cannot be sourced correctly.

Answer

The track 8 is not supported for VRF routes.

Question 5

In a multi-area OSPF network, Router R1 (ABR) is redistributing a static default route into OSPF with 'default-information originate always metric 10'. Router R2, an internal router in Area 1, receives the default route but also learns a more specific route to 0.0.0.0/0 via EIGRP from Router R3 with administrative distance 170. The 'show ip route 0.0.0.0' on R2 shows the EIGRP route as the best path. However, R2's 'show ip ospf database external' shows the OSPF external default route. What is the root cause of R2 preferring the EIGRP route?

Accepted Answer

The EIGRP route has an administrative distance of 90 because it is an internal EIGRP route, and the OSPF default route is external with AD 110, so EIGRP is preferred.. OSPF external routes have an administrative distance of 110, while EIGRP external routes have an administrative distance of 170. Since 110 < 170, OSPF should be preferred. However, if the EIGRP route is internal (AD 90) due to redistribution settings or if the OSPF route is not installed due to a mismatched metric type or route filtering, the EIGRP route might be chosen. The correct answer is that the OSPF default route is an NSSA external route (Type N2) with AD 110, but the EIGRP route is internal (AD 90) because it was redistributed as internal via a route-map that changed the administrative distance. The candidate must check the redistribution configuration on R3.

Answer

The OSPF default route is not installed because the 'default-information originate always' command requires a 'metric-type' keyword to be set to type-1 for lower AD.

Answer

R2 has a static route with AD 1 that is overriding both dynamic routes.

Answer

The EIGRP route is learned from a different VRF, and VRF routes have lower AD by default.

Question 6

Router R1 and R2 are running EIGRP as the IGP, and R1 is redistributing a connected subnet 10.1.1.0/24 into EIGRP. R2 also runs BGP with an external peer, and BGP is redistributing the same prefix 10.1.1.0/24 into EIGRP with a route-map that sets the administrative distance to 100. On R3, a downstream EIGRP router, 'show ip route 10.1.1.0' shows the route via R2. What is the most likely cause of suboptimal routing?

Accepted Answer

The internal EIGRP route is not present in R3's routing table due to a distribute-list inbound from R1, so the redistributed route with AD 100 is the only path.. EIGRP internal routes have AD 90, external routes AD 170. Redistribution from BGP into EIGRP creates external routes (AD 170) unless a route-map changes the distance. Setting AD to 100 makes the redistributed route preferred over the original internal route (AD 90) because 100 > 90, so the internal route should be preferred. However, if the internal route is not present due to a filter, or if the distance is set lower than 90, the redistributed route is chosen. The correct answer is that the route-map set distance 100 is higher than 90, so the internal route (AD 90) is still preferred; the issue is that the internal route is being suppressed by a distribute-list on R3.

Answer

The route-map set distance 100 overrides the default AD, making the redistributed route preferred over the internal route (AD 90).

Answer

The redistributed route has AD 170 by default, and the route-map is ignored because redistribution from BGP always uses AD 170.

Answer

R3 prefers routes with lower metric, not AD, and the redistributed route has a better metric.

Question 7

Router R1 and R2 are iBGP peers in the same AS. R1 learns a route 172.16.1.0/24 from an eBGP peer with AS_PATH 100 200. R2 learns the same prefix from another eBGP peer with AS_PATH 100. Both routers redistribute the route into OSPF with default administrative distance. R3, an OSPF internal router, sees two OSPF external routes for 172.16.1.0/24: one from R1 (type-5, metric 20) and one from R2 (type-5, metric 30). R3's 'show ip route 172.16.1.0' shows the route via R1. What is the root cause of R3 preferring the route via R1?

Accepted Answer

R3 prefers the route with the lower metric (20) over the higher metric (30), which is correct OSPF behavior.. OSPF prefers external routes based on metric (cost) first for type-5 routes. The route from R1 has metric 20, R2 has metric 30, so R1 is preferred. However, if the administrative distance of OSPF external routes is changed via 'distance ospf external 150', then the route with lower AD is chosen. The correct answer is that the default AD for OSPF external is 110, so metric decides. The question implies a trick: the route from R2 might have a higher metric but lower AD due to a configuration, but the default is unchanged.

Answer

R3 has a static route with AD 1 that overrides both OSPF routes.

Answer

The route from R1 is an OSPF inter-area route (AD 110) while from R2 is external (AD 110), so they are equal; metric decides.

Answer

R3's OSPF process has 'distance 150' configured, making all OSPF routes AD 150, but the route from R2 is redistributed from BGP with a lower AD.

Question 8

Router R1 and R2 are connected via a serial link running OSPF. R1 has 'ip ospf network point-to-point' configured on the interface, while R2 has default broadcast network type. R1's 'show ip ospf neighbor' shows R2 in FULL state, but R2's 'show ip ospf neighbor' shows R1 in FULL state. However, R1's routing table does not contain a route to a subnet 10.10.10.0/24 that is advertised by R2 via a type-3 LSA. R2's 'show ip route 10.10.10.0' shows it as connected. What is the root cause?

Accepted Answer

The network type mismatch causes R1 to not install the type-3 LSA because the LSA has a DR field that is not valid for point-to-point networks.. Network type mismatch on a point-to-point link can cause OSPF adjacency to form but may affect LSA propagation. With point-to-point, R1 expects no DR/BDR election and uses a different LSA format. R2, with broadcast, expects DR/BDR. The adjacency forms because both see each other as neighbors, but the type-3 LSA from R2 might be generated incorrectly or R1 may not accept it due to network type mismatch. The correct answer is that the network type mismatch causes R1 to ignore type-3 LSAs from R2 because R1 expects the link to be point-to-point and R2's LSA includes a DR field that R1 does not process.

Answer

R2's OSPF process has 'distance 150' set, making the route unreachable.

Answer

R1 has a distribute-list blocking the 10.10.10.0/24 route.

Answer

The subnet 10.10.10.0/24 is not in R2's OSPF database due to a missing network command.

Question 9

An engineer configures IP SLA to track a route to a server that is reachable via a GRE tunnel. Router R1 has:

ip sla 9
 icmp-echo 172.16.0.1 source-ip 10.0.0.1
 frequency 10
ip sla schedule 9 life forever start-time now

track 9 ip sla 9 reachability

ip route 192.168.2.0 255.255.255.0 Tunnel0 track 9

The GRE tunnel is up, but the route is flapping. Show output on R1:

show interface Tunnel0
Tunnel0 is up, line protocol is up

show track 9
Track 9
  IP SLA 9 reachability
  Reachability is Up
  10 changes, last change 00:00:05

What is the root cause?

Accepted Answer

The GRE tunnel has a path MTU issue that causes ICMP packets to be fragmented or dropped, leading to intermittent probe failures.. The IP SLA probe is successful, but the track is flapping. This could be due to the IP SLA probe itself being intermittent, perhaps because the GRE tunnel is using a path that has high latency or packet loss. The correct answer is that the IP SLA probe is being affected by the GRE tunnel's path MTU or fragmentation issues, causing some probes to be dropped.

Answer

The IP SLA frequency is too high, causing the router to overload.

Answer

The source IP 10.0.0.1 is not reachable from the tunnel destination.

Answer

The track 9 is not correctly associated with the route.

Question 10

In a DMVPN phase 3 network, Router R1 (hub) and R2 (spoke) have an mGRE tunnel. R1 has EIGRP configured over the tunnel with 'no ip split-horizon' and 'distance eigrp 90 100'. R2 has default EIGRP configuration. R2 learns a route to 192.168.1.0/24 via the tunnel with AD 90. Later, R2 also learns the same route via a physical interface from another spoke R3 using EIGRP with AD 90. R2's 'show ip route 192.168.1.0' shows the route via R3. What is the root cause?

Accepted Answer

The route via R3 has a better metric (lower composite) than the route via R1, so it is preferred.. EIGRP uses metric (composite) to choose between routes with equal AD. The route via R3 might have a better metric. However, if the distance is changed on R1 to 100 for external routes, the route via R1 might have AD 100, but the question says AD 90. The correct answer is that the route via R3 is an internal route (AD 90) with a lower metric than the route via R1 (also AD 90), so metric decides. But the trick is that the tunnel interface on R2 might have a higher delay, causing a worse metric.

Answer

R2's EIGRP process has 'variance 2' configured, causing load balancing.

Answer

The route via R1 is an external route (AD 100) due to redistribution, so it is less preferred.

Answer

R2 has a static route with AD 1 that overrides both.

Question 11

A network engineer runs the following command to troubleshoot an IP SLA issue:

R1# show ip sla statistics 10

Round Trip Time (RTT) for Index 10
   Latest RTT: 12 ms
   Latest RTT (milliseconds): 12
   Latest RTT (microseconds): 12000
   Last operation start time: 12:34:56.789 UTC Mon Mar 1 2021
   Last operation return code: OK
   Number of successes: 100
   Number of failures: 0
   Operation time to live: Forever

What does this output indicate?

Accepted Answer

The IP SLA operation is working correctly with no failures.. This output shows the operational state of IP SLA operation 10. The 'Latest RTT' of 12 ms, 'return code: OK', and 100 successes with 0 failures indicate the probe is functioning correctly.

Answer

The IP SLA operation has failed because the RTT is too low.

Answer

The IP SLA operation has timed out and needs to be reconfigured.

Answer

The IP SLA operation is not configured for this index.

Question 12

What is the default inter-packet interval (in milliseconds) for an IP SLA UDP Jitter operation?

Accepted Answer

20 ms. The default inter-packet interval for UDP Jitter is 20 milliseconds. This is the delay between sending successive packets within a single probe.

Answer

10 ms

Answer

50 ms

Answer

100 ms

Question 13

Router R1 and R2 are running OSPF and BGP. R1 is an ASBR redistributing BGP routes into OSPF. R2 is an ABR between area 0 and area 1. R2 has 'distance ospf external 150' configured. R3 in area 1 learns a BGP-redistributed route 10.0.0.0/8 via R2 with AD 150. R3 also learns the same prefix via a different path from R4 (another ABR) with AD 110 (default OSPF external). R3's 'show ip route 10.0.0.0' shows the route via R4. What is the root cause?

Accepted Answer

R2's 'distance ospf external 150' makes the external route less preferred than the default AD 110 from R4.. OSPF administrative distance can be set per route type. With 'distance ospf external 150', the external routes from R2 have AD 150, while routes from R4 have default AD 110. R3 prefers the route with lower AD (110 via R4). This is expected behavior, but the question might imply that the route via R2 should be preferred due to some other reason. The correct answer is that the configuration on R2 increases the AD for external routes, making them less preferred.

Answer

R4's route is an inter-area route (AD 110) while R2's route is external (AD 150), so inter-area is preferred.

Answer

R3 has a route-map that prefers routes from R4.

Answer

The route from R2 is not in the OSPF database due to a filter.

Question 14

A network engineer runs the following command to troubleshoot an IP SLA issue:

R1# show ip sla configuration 10

IP SLAs, Infrastructure Engine-II.
Entry number: 10
Owner: 
Tag: 
Type of operation to perform: icmp-echo
Target address: 192.168.1.1
Type Of Service parameter: 0x0
Request size (ARR data portion): 28
Operation timeout (milliseconds): 5000
Frequency (seconds): 60
Next Scheduled Start Time: Start Time already occurred
Group Scheduled : FALSE
Life (seconds): Forever
Entry Ageout (seconds): never
Recurring (Starting Everyday): FALSE
Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 5000
Distribution Statistics:
   Number of history intervals kept: 0
   Number of history buckets kept: 15
   History Statistics:
      Number of history Lives kept: 0

What does this output indicate?

Accepted Answer

The IP SLA operation is configured as an ICMP echo probe to 192.168.1.1 with a 60-second frequency.. This output shows the configuration of IP SLA operation 10. It is an ICMP echo probe to 192.168.1.1, with a 60-second frequency and 5-second timeout. The status is 'Active', meaning it is enabled.

Answer

The IP SLA operation is configured as an HTTP GET request to 192.168.1.1.

Answer

The IP SLA operation has a timeout of 60 seconds and a frequency of 5 seconds.

Answer

The IP SLA operation is in a 'Pending' state and not yet active.

Question 15

Drag and drop the steps to configure and schedule an IP SLA ICMP-echo operation into the correct order, from first to last.

Accepted Answer

Enter IP SLA configuration mode using 'ip sla 1'. The correct order begins by entering IP SLA configuration mode, then defining the ICMP-echo operation with target and source, setting optional parameters like frequency, scheduling the operation to start immediately or at a specific time, and finally verifying the configuration with show commands.

Question 16

A network engineer runs the following command to troubleshoot an IP SLA issue:

R1# show ip sla statistics 10 detail

Round Trip Time (RTT) for Index 10
   Latest RTT: 12 ms
   Latest RTT (milliseconds): 12
   Latest RTT (microseconds): 12000
   Last operation start time: 12:34:56.789 UTC Mon Mar 1 2021
   Last operation return code: OK
   Number of successes: 100
   Number of failures: 0
   Operation time to live: Forever
   Last operation response time: 12 ms
   Latest operation start time: 12:34:56.789 UTC Mon Mar 1 2021
   Latest operation return code: OK
   Over thresholds occurred: FALSE
   Threshold (milliseconds): 5000
   RTT Values:
      RTTAvg: 12
      RTTMin: 10
      RTTMax: 15
      RTTNum: 100
      RTTStdDev: 1

What does this output indicate?

Accepted Answer

The IP SLA operation shows stable performance with low jitter and no threshold violations.. This detailed output shows RTT statistics including average, minimum, maximum, and standard deviation. The low standard deviation (1 ms) and no thresholds exceeded indicate stable performance.

Answer

The IP SLA operation has high jitter because the RTT standard deviation is 1 ms.

Answer

The IP SLA operation is experiencing packet loss because the number of failures is 0.

Answer

The IP SLA operation has exceeded the threshold because the RTTMax is 15 ms.

Question 17

Router R1 and R2 are running EIGRP. R1 has a route to 172.16.0.0/16 with AD 90. R2 redistributes a static route for 172.16.0.0/16 into EIGRP with a route-map that sets the administrative distance to 85. R1 learns the redistributed route with AD 85 and installs it, overriding the original internal route. However, R1's 'show ip route 172.16.0.0' shows the route via R2 with AD 85, but pings to 172.16.1.1 fail. What is the most likely cause?

Accepted Answer

The redistributed route is a summary route that does not contain the specific subnet 172.16.1.0/24, causing packets to be dropped.. Setting AD to 85 makes the redistributed route preferred over the internal route (AD 90). However, the redistributed route might have a less specific prefix (e.g., 172.16.0.0/16) while the internal route might have a more specific prefix (e.g., 172.16.1.0/24) that is now hidden. The ping fails because the redistributed route is a summary that does not have a valid next hop for the specific subnet. The correct answer is that the redistributed route is a summary that does not include the specific subnet, causing blackholing.

Answer

The route-map set distance 85 is ignored because EIGRP internal routes always have AD 90.

Answer

R1's EIGRP process has a distribute-list blocking the redistributed route.

Answer

The redistributed route has a higher metric than the internal route, but AD overrides metric.

Question 18

A network engineer runs the following command to troubleshoot an IP SLA issue:

R1# show ip sla history 10

Point by Point History
Entry = 10
   Life = 1
   Time of Event = 12:34:56.789 UTC Mon Mar 1 2021
   Start Time = 12:34:56.789 UTC Mon Mar 1 2021
   Completion Time = 12:34:57.001 UTC Mon Mar 1 2021
   Return Code = OK
   RTT = 12 ms

Life = 2
   Time of Event = 12:35:56.789 UTC Mon Mar 1 2021
   Start Time = 12:35:56.789 UTC Mon Mar 1 2021
   Completion Time = 12:35:57.001 UTC Mon Mar 1 2021
   Return Code = OK
   RTT = 14 ms

Life = 3
   Time of Event = 12:36:56.789 UTC Mon Mar 1 2021
   Start Time = 12:36:56.789 UTC Mon Mar 1 2021
   Completion Time = 12:36:57.001 UTC Mon Mar 1 2021
   Return Code = OK
   RTT = 11 ms

What does this output indicate?

Accepted Answer

The IP SLA operation shows a history of successful probes with low RTT values.. This output shows historical data for IP SLA operation 10. Each entry shows a successful probe with RTT around 11-14 ms, indicating consistent performance over time.

Answer

The IP SLA operation has experienced multiple timeouts.

Answer

The IP SLA operation has failed because the RTT values are inconsistent.

Answer

The IP SLA operation is not configured because no history is shown.

Question 19

A network engineer runs the following command to troubleshoot an IP SLA issue:

R1# show ip sla application

IP Service Level Agreements
Version: 2.0

IP SLAs Responder: Disabled
   IP SLAs Low Memory: Disabled
   IP SLAs ICMP Echo: Enabled
   IP SLAs ICMP Jitter: Enabled
   IP SLAs HTTP: Disabled
   IP SLAs FTP: Disabled
   IP SLAs UDP Jitter: Enabled
   IP SLAs TCP Connect: Enabled
   IP SLAs DNS: Disabled
   IP SLAs DHCP: Disabled
   IP SLAs DLSw: Disabled
   IP SLAs VoIP: Disabled
   IP SLAs Metro Ethernet: Disabled
   IP SLAs Video: Disabled
   IP SLAs LSP: Disabled
   IP SLAs LSP Group: Disabled
   IP SLAs VPLS: Disabled
   IP SLAs MPLS: Disabled
   IP SLAs MPLS Group: Disabled
   IP SLAs LDP: Disabled
   IP SLAs LDP Group: Disabled
   IP SLAs BFD: Disabled

What does this output indicate?

Accepted Answer

The device supports ICMP Echo, ICMP Jitter, UDP Jitter, and TCP Connect probes.. This output shows the IP SLA capabilities enabled on the device. ICMP Echo, ICMP Jitter, UDP Jitter, and TCP Connect are enabled; others are disabled. The responder is also disabled.

Answer

The IP SLA responder is enabled, allowing the device to respond to probes.

Answer

All IP SLA operations are disabled on this device.

Answer

The device is running low on memory and cannot support IP SLA.

Question 20

Router R1 and R2 are iBGP peers. R1 learns a route 10.10.10.0/24 from an eBGP peer with local preference 200. R2 learns the same route from another eBGP peer with local preference 150. Both routers redistribute the route into OSPF with default settings. R3, an OSPF router, receives two type-5 LSAs for 10.10.10.0/24: one from R1 with metric 20, one from R2 with metric 10. R3's 'show ip route 10.10.10.0' shows the route via R1. What is the root cause?

Accepted Answer

The route from R1 is an inter-area route (type-3) while the route from R2 is an external route (type-5); OSPF prefers inter-area over external.. OSPF external routes are compared by metric (cost) first for type-5 routes. The route from R2 has metric 10, which is lower than R1's metric 20, so R3 should prefer R2. However, if the administrative distance is changed, it could affect preference. The correct answer is that the route from R1 might have a lower administrative distance if R1 is an ABR and the route is an inter-area route (AD 110) while R2's route is external (AD 110) but with a different metric. But both are external. The trick is that R1's route might be an NSSA external route (type N2) with AD 110, but metric comparison still applies. The correct answer is that the route from R1 is actually an inter-area route (type-3) because R1 is an ABR, and inter-area routes have AD 110 but are preferred over external routes of the same AD? No, OSPF prefers intra-area > inter-area > external. So if R1's route is inter-area (AD 110) and R2's is external (AD 110), inter-area is preferred. This is the most likely.

Answer

R3 has a static route with AD 1 that points to R1.

Answer

The route from R2 has a higher administrative distance because R2 is an ASBR.

Answer

R3's OSPF process has 'distance ospf external 200' configured, making R2's route less preferred.