350-401 IP SLA — Timed 15 Questions

Question 1

A network engineer configures an IP SLA on a Cisco router to monitor reachability to a critical server at 10.1.1.1 using ICMP echo. The IP SLA is used as a track object for a static default route. After deployment, the engineer notices that the static route is never removed from the routing table, even when the server is unreachable. The IP SLA operation shows 'State: Active' and 'Latest RTT: NoConnection/Busy/Timeout'. What is the most likely cause?

Accepted Answer

The IP SLA operation needs a threshold configured to mark the operation as 'down' when the RTT exceeds the threshold or a timeout occurs.. The IP SLA operation is not failing because the threshold has not been configured. Without a threshold, the operation never transitions to a 'down' state, so the track object never triggers the removal of the static route.

Answer

The IP SLA operation is not configured with a timeout value, so it never times out.

Answer

The track object must be configured with a 'down' delay to allow the route to be removed.

Answer

The static route must be configured with a higher administrative distance to allow the IP SLA to remove it.

Question 2

An engineer configures IP SLA 100 to monitor the jitter and latency of a VoIP call path between two branch routers. The configuration uses UDP jitter with a target of 192.168.2.2 on port 16384. The engineer notices that the IP SLA operation shows 'State: Active' but no jitter or latency statistics are collected. The router is generating the probe packets, but the remote router does not respond. What is the most likely reason?

Accepted Answer

The remote router must have an IP SLA responder configured to process the UDP jitter probes.. UDP jitter probes require a responder on the destination router to echo the packets back. Without the responder, the source router sends probes but receives no response, so no jitter statistics can be computed.

Answer

The IP SLA operation must be configured with a 'request-data-size' value to match the remote router's MTU.

Answer

The source router needs a 'frequency' setting that matches the remote router's response interval.

Answer

The firewall on the remote router is blocking the UDP port 16384, preventing the probe from reaching the target.

Question 3

A network engineer configures IP SLA 1 to monitor HTTP server availability at 10.1.1.1 using HTTP GET. The operation is used as a track object for a backup static route. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 200 ms', but the track object shows 'Track 1: up' even though the HTTP server returns a 404 error. What is the cause?

Accepted Answer

The IP SLA HTTP operation does not interpret HTTP status codes by default; it only checks if a TCP connection is established.. By default, IP SLA HTTP operations consider a successful HTTP response (any status code) as a success. The operation does not fail on 404 unless a specific status code match is configured.

Answer

The IP SLA HTTP operation must be configured with a 'url' that includes the full path, otherwise it defaults to the root and returns 404.

Answer

The track object must be configured with a 'down' threshold to trigger when the HTTP response time exceeds a value.

Answer

The HTTP server is responding, so the IP SLA operation correctly shows success; the engineer must use a different type of probe, like TCP connect, to detect the 404.

Question 4

An engineer configures IP SLA 10 to monitor the reachability of a next-hop router at 10.1.1.1 using ICMP echo. The IP SLA is used as a track object for a static route. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 1 ms', but the track object shows 'Track 10: up' even though the next-hop router is actually unreachable from the source. The source router has a default route pointing to 10.1.1.1. What is the most likely cause?

Accepted Answer

The IP SLA operation is using the wrong source IP address; it should be sourced from the interface that connects to the next-hop router.. If the source router has a default route pointing to the same next-hop, the IP SLA probe packets may be sent out using that default route, which could lead to the probe being sent to a different path or looping. However, the more direct cause is that the IP SLA probe is sourced from an interface that is not the one that would be used to reach the next-hop, so the probe may succeed even if the next-hop is unreachable via the expected path.

Answer

The IP SLA operation must be configured with a 'timeout' value lower than the RTT to force a failure.

Answer

The track object must be configured with a 'down' delay to prevent flapping.

Answer

The static route must be configured with a higher administrative distance to allow the IP SLA to remove it.

Question 5

A network engineer configures IP SLA 20 to monitor the response time of a DNS server at 10.1.1.1 using DNS query for 'example.com'. The operation is used to influence routing decisions. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 50 ms', but the DNS server is actually down and not responding to any queries. What is the most likely reason?

Accepted Answer

The IP SLA DNS probe is using a cached DNS response from the router's DNS resolver, so it does not actually query the server.. The DNS probe may be receiving a response from a cache (either on the router itself or an intermediate DNS cache) rather than the actual DNS server. This can cause the probe to succeed even if the server is down.

Answer

The IP SLA DNS probe must be configured with a 'timeout' value lower than 50 ms to detect the failure.

Answer

The DNS server is responding to the probe but not to other queries because the probe uses a different port.

Answer

The IP SLA operation is configured with a 'frequency' that is too low, causing the probe to be sent before the server times out.

Question 6

An engineer configures IP SLA 30 to monitor the one-way delay to a remote site using UDP jitter. The operation is used to adjust routing metrics via route maps. The engineer notices that the IP SLA operation shows 'State: Active' but the one-way delay values are inconsistent, sometimes showing negative values. What is the most likely cause?

Accepted Answer

The source and destination routers do not have synchronized clocks via NTP, causing one-way delay calculations to be inaccurate.. One-way delay measurements require clock synchronization between the source and destination routers. Without NTP, the clocks may drift, causing negative or inaccurate delay values.

Answer

The IP SLA operation is not configured with a 'request-data-size' that matches the remote router's MTU, causing fragmentation and delay variations.

Answer

The IP SLA operation is using a 'frequency' that is too high, causing the probes to overlap and corrupt the statistics.

Answer

The remote router's IP SLA responder is not configured, so the source is using a different method to estimate delay.

Question 7

A network engineer configures IP SLA 40 to monitor the reachability of a server at 10.1.1.1 using ICMP echo. The operation is used as a track object for a static route. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 10 ms', but the track object shows 'Track 40: down'. The engineer checks the track configuration and sees 'track 40 ip sla 40 reachability'. What is the most likely cause?

Accepted Answer

The IP SLA operation has a threshold configured that is lower than the RTT, causing the operation to be marked as 'down'.. The track object is configured to track reachability, which means it checks if the IP SLA operation is in a 'down' state. However, if the IP SLA operation is active, the track object should be up. The most likely cause is that the IP SLA operation is configured with a threshold that is being exceeded, causing the operation to be considered 'down' even though it is active.

Answer

The track object must be configured with 'ip sla 40 state' instead of 'reachability' to match the operation state.

Answer

The IP SLA operation is not configured with a 'frequency', so it only runs once and then goes down.

Answer

The static route is configured with a higher administrative distance, causing the track object to go down.

Question 8

An engineer configures IP SLA 50 to monitor the response time of a TCP connection to a server at 10.1.1.1 on port 80. The operation is used to trigger a backup path. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 100 ms', but the server is actually down and not responding to TCP SYN packets. What is the most likely reason?

Accepted Answer

A stateful firewall or load balancer is responding to the TCP SYN on behalf of the server, causing the probe to succeed.. The TCP connect probe only checks if the TCP three-way handshake completes. If the server is down but a stateful firewall or load balancer responds to the SYN with a SYN-ACK, the probe will succeed even if the server is down.

Answer

The IP SLA TCP connect probe does not actually verify that the server responds; it only checks if the port is open.

Answer

The IP SLA operation must be configured with a 'timeout' value lower than 100 ms to detect the failure.

Answer

The server is actually responding to the probe but not to other traffic because the probe uses a different source IP.

Question 9

A network engineer configures IP SLA 60 to monitor the jitter of a VoIP call path between two sites. The operation uses UDP jitter with a target of 192.168.3.3 on port 16384. The engineer notices that the IP SLA operation shows 'State: Active' and 'Latest RTT: 10 ms', but the jitter values are all zero. The remote router has an IP SLA responder configured. What is the most likely cause?

Accepted Answer

The IP SLA operation is configured with a 'num-packets' value of 1, so only one packet is sent per probe, and jitter cannot be calculated.. Jitter is calculated as the variation in delay between consecutive packets. If only one probe packet is sent per operation, there is no variation to measure, so jitter will be zero. The IP SLA UDP jitter operation must send multiple packets per probe to calculate jitter.

Answer

The remote router's IP SLA responder is not configured to calculate jitter, only to echo packets.

Answer

The IP SLA operation is using a 'frequency' that is too high, causing the probes to be sent too quickly and jitter to be zero.

Answer

The network path has no variable delay, so jitter is naturally zero.

Question 10

A network engineer runs the following command on Router R1:

R1# show ip sla summary

IPSLAs Latest Operation Summary
Codes: * active, ^ inactive, ~ pending

ID       Type         Destination       Stats       Return Code      Last
1        icmp-echo    192.168.1.10      Success     OK               1
2        icmp-echo    192.168.1.20      Success     OK               2
3        udp-jitter   192.168.1.30      Success     OK               3
*4       icmp-echo    192.168.1.40      Success     OK               10

Based on this output, what can be concluded?

Accepted Answer

IP SLA operation 4 is currently active.. The asterisk (*) next to ID 4 indicates that this IP SLA operation is currently active. The other operations are not marked as active, meaning they are either configured but not running or have been stopped.

Answer

All IP SLA operations are active.

Answer

IP SLA operation 3 has failed.

Answer

IP SLA operation 1 has the highest round-trip time.

Question 11

A network engineer executes the following command on Router R2:

R2# show ip sla configuration 1

IP SLAs Infrastructure Engine-II
Entry number: 1
Owner: admin
Tag:
Type of operation to perform: icmp-echo
Target address: 192.168.2.10
Source address: 192.168.2.1
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 passed
Group Scheduled : FALSE
Life (seconds): Forever
Entry Ageout (seconds): never
Recurring (Starting Everyday, Starting Time: 00:00:01)
Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 5000
Distribution Statistics:
Number of statistic hours kept: 2
Number of statistic distribution buckets kept: 1
Statistic distribution interval (milliseconds): 20
Enhanced History:

Based on this output, what is the frequency of the IP SLA operation?

Accepted Answer

60 seconds. The 'Frequency (seconds): 60' line indicates that the IP SLA operation runs every 60 seconds.

Answer

30 seconds

Answer

120 seconds

Answer

5000 milliseconds

Question 12

A network engineer issues the following command on Router R3:

R3# show ip sla statistics 2

Round Trip Time (RTT) for Index 2
Latest RTT: 12 ms
Latest RTT: NoConnection/Busy/Timeout
Latest Operation Start Time: 12:00:00.000 UTC Mon Mar 1 2021
Latest Operation Return Code: Timeout
Number of successes: 45
Number of failures: 5
Over thresholds: 0

Based on this output, what is the most likely issue?

Accepted Answer

The most recent probe timed out, indicating a possible connectivity issue.. The 'Latest Operation Return Code: Timeout' indicates that the most recent probe did not receive a response, suggesting a connectivity problem to the target. The presence of both successes and failures shows intermittent issues.

Answer

The IP SLA operation has never succeeded.

Answer

The target is unreachable due to a persistent failure.

Answer

The round-trip time is 12 ms, which is above the threshold.

Question 13

A network engineer runs the following command on Router R4:

R4# show ip sla monitor statistics 3

Round Trip Time (RTT) for Index 3
Latest RTT: 25 ms
Latest Operation Start Time: 14:30:00.000 UTC Mon Mar 1 2021
Latest Operation Return Code: OK
Number of successes: 100
Number of failures: 0
Over thresholds: 0

Based on this output, what can be concluded about the IP SLA operation?

Accepted Answer

The operation is working correctly with no failures.. The return code 'OK' and zero failures indicate that the operation is functioning correctly and the target is reachable.

Answer

The operation has experienced failures.

Answer

The operation is currently failing.

Answer

The round-trip time exceeds the threshold.

Question 14

A network engineer executes the following command on Router R5:

R5# show ip sla monitor configuration 4

IP SLAs Monitor Configuration
Entry number: 4
Owner:
Tag:
Type of operation to perform: udp-jitter
Target address: 192.168.5.10
Target port: 16384
Source address: 192.168.5.1
Source port: 0
Type Of Service parameter: 0x0
Request size (ARR data portion): 32
Operation timeout (milliseconds): 5000
Frequency (seconds): 60
Next Scheduled Start Time: Start Time already passed
Group Scheduled : FALSE
Life (seconds): Forever
Entry Ageout (seconds): never
Recurring (Starting Everyday, Starting Time: 00:00:01)
Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 5000
Distribution Statistics:
Number of statistic hours kept: 2
Number of statistic distribution buckets kept: 1
Statistic distribution interval (milliseconds): 20
Enhanced History:

Based on this output, what type of IP SLA operation is configured?

Accepted Answer

UDP jitter. The line 'Type of operation to perform: udp-jitter' clearly indicates the operation type is UDP jitter.

Answer

ICMP echo

Answer

TCP connect

Answer

HTTP get

Question 15

A network engineer issues the following command on Router R6:

R6# show ip sla statistics 5

Round Trip Time (RTT) for Index 5
Latest RTT: 150 ms
Latest Operation Start Time: 16:00:00.000 UTC Mon Mar 1 2021
Latest Operation Return Code: OK
Number of successes: 10
Number of failures: 0
Over thresholds: 8

Based on this output, what does the 'Over thresholds: 8' indicate?

Accepted Answer

8 probes had RTT exceeding the configured threshold.. The 'Over thresholds' counter shows how many times the RTT exceeded the configured threshold. In this case, 8 out of 10 successful probes had RTT above the threshold, indicating high latency even though the operation succeeded.

Answer

8 probes failed to reach the target.

Answer

8 probes were sent in total.

Answer

The threshold is set to 150 ms.