75 of 76 questions · Page 1/2 · IP Sla topic · Answers revealed
What is the default timeout value (in milliseconds) for an IP SLA operation?
The default timeout is 5000 ms.
Why this answer
The default timeout for IP SLA operations is 5000 milliseconds (5 seconds). If no response is received within this time, the probe is considered failed.
An engineer configured IP SLA 40 with a UDP echo probe to monitor a remote server port 80. The IP SLA is used in a track object for a backup static route. The engineer observes that the IP SLA state is 'Timeout' even though the server is reachable via ping from the router. What is the most likely cause?
UDP echo probes expect a UDP service on the target port. Port 80 is typically TCP, so the probe times out.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 3 Round Trip Time (RTT) for Index 3 Latest RTT: 150 ms Latest RTT (milliseconds): 150 Latest RTT (microseconds): 150000 Number of successes: 80 Number of failures: 20 Operation time to live: Forever Output: OK R1# show track 1 Track 1 IP SLA 3 reachability Reachability is Up 2 changes, last change 00:00:10 Latest operation return code: OK Latest RTT (milliseconds): 150 Tracked by: ip route 0.0.0.0 0.0.0.0 192.168.1.1 track 1 Based on this output, which statement is correct?
The track shows 'Up', meaning the IP SLA is reachable, and the static route is installed.
Why this answer
The track shows 'Reachability is Up' based on IP SLA 3. The IP SLA statistics show successes and failures, but the latest return code is OK, so the track is up. This means the static route is active.
The failures (20) indicate some probes failed, but the track still considers it reachable because the threshold for reachability is likely based on a percentage or consecutive failures.
A network engineer configures IP SLA with a UDP echo operation to monitor a remote server. The IP SLA responder is configured on the remote router. The engineer notices that the operation shows 'Timeout' intermittently, but standard UDP connectivity tests from the router to the server succeed. The engineer checks the IP SLA responder configuration and finds that the control port is set to a non-default value. Which is the most likely explanation?
The control port mismatch causes the initiator to fail to establish the operation, leading to timeouts.
Why this answer
IP SLA UDP echo operations require the IP SLA responder to be configured with the correct control port. If the responder uses a non-default control port, the initiator must be configured to use that port using the 'control' keyword under the IP SLA operation. Without this, the initiator uses the default control port (1967), causing communication failures and intermittent timeouts.
A network engineer configures IP SLA with an HTTP GET operation to monitor a web server. The operation shows 'Success' but the response time is extremely high. The engineer checks the web server and finds it is overloaded. The engineer wants to configure a threshold so that the IP SLA operation triggers a track object when the response time exceeds 500 ms. Which configuration change is required?
The track object must be configured to monitor the threshold state using the 'threshold' keyword; otherwise, it only tracks reachability.
Why this answer
IP SLA HTTP operations measure response time, but to trigger a track object based on threshold violation, the engineer must configure the 'threshold' command under the IP SLA operation and then configure the track object to react to the 'threshold' state, not just the 'up/down' state. By default, track objects only track up/down, not threshold violations.
An engineer configures IP SLA with a UDP jitter operation to monitor VoIP quality between two routers. The operation shows 'OverThreshold' in the show ip sla statistics output, but the engineer notices that the IP SLA responder on the remote router is configured with a control port that does not match the default. Which is the most likely explanation?
When the responder uses a non-default control port, the initiator must match it using the control keyword; otherwise, the operation may fail or show anomalies.
Why this answer
IP SLA UDP jitter operations require the IP SLA responder to be configured with the correct control port; if the responder uses a non-default control port, the IP SLA initiator must be configured to use that port via the 'control' keyword under the IP SLA operation, otherwise the operation fails or produces incorrect results.
An engineer must configure IP SLA tracking to trigger a static route removal when a remote server becomes unreachable. Which TWO configuration steps are required? (Choose TWO.)
Correct. This creates and schedules the IP SLA operation, which is the first step.
Why this answer
To track IP SLA reachability, you must first create an IP SLA operation (e.g., type icmp-echo) and schedule it. Then, create a track object that references the IP SLA operation's return code. Finally, apply the track to the static route using the 'track' keyword.
The 'reaction' configuration is optional for basic tracking.
A network engineer runs the following command to troubleshoot an IP SLA issue: R1# show ip sla monitor configuration 10 IP SLAs Monitor, 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?
The configuration matches these parameters.
Why this answer
This is the older 'ip sla monitor' configuration output, identical to 'ip sla configuration'. It shows an ICMP echo probe to 192.168.1.1, active status, 60-second frequency, and 5-second timeout.
Which TWO commands can be used to verify the operational state and statistics of an IP SLA operation? (Choose TWO.)
Correct. This command displays detailed statistics such as RTT, packet loss, and jitter for each IP SLA operation.
Why this answer
The 'show ip sla statistics' command displays detailed statistics for all IP SLA operations, including RTT, packet loss, and jitter. The 'show ip sla configuration' command shows the configuration parameters, not real-time state. 'show track' shows the state of track objects, not the IP SLA operation directly. 'show ip sla summary' provides a one-line summary of each operation's state. 'debug ip sla trace' is a debug command, not a verification show command.
Which TWO commands can be used to verify IP SLA operations on a Cisco IOS device? (Choose TWO.)
Displays the latest statistics for each configured IP SLA operation.
Why this answer
The 'show ip sla statistics' command displays the latest statistics for each IP SLA operation, and 'show ip sla reaction-configuration' shows the threshold and reaction settings. 'show ip sla configuration' shows the configuration but not live statistics. 'show ip sla monitor' is a legacy command not used in modern IOS. 'show ip sla summary' is not a valid command.
Which TWO statements about IP SLA responder configuration are true? (Choose TWO.)
Correct. UDP jitter probes require the responder to timestamp the packets for accurate delay and jitter calculations.
Why this answer
The IP SLA responder is a component that listens for probe requests and sends replies. It is required for certain probe types like UDP jitter and TCP connect to ensure accurate measurements. The responder must be enabled on the destination device with the 'ip sla responder' global command.
It does not require a specific port for ICMP echo, and it does not automatically adjust timestamps without the 'timestamp' option.
Which IP SLA operation type is specifically designed to measure one-way delay, jitter, and packet loss using UDP packets with sequence numbers and timestamps?
Correct. UDP Jitter is designed for one-way delay, jitter, and packet loss measurement.
Why this answer
The UDP Jitter operation (type 3) sends UDP packets with embedded sequence numbers and timestamps to measure one-way delay, jitter, and packet loss between source and destination.
Which TWO configuration steps are required to use IP SLA for tracking an object in a routing protocol like EIGRP? (Choose TWO.)
The IP SLA operation must be defined first to generate the probe data.
Why this answer
To use IP SLA for routing protocol tracking, you must first configure an IP SLA operation (e.g., ICMP echo) and then create a tracking object that references the IP SLA operation. The tracking object is then used in the routing protocol configuration (e.g., 'track 1 ip sla 1 reachability'). Configuring a static route or a prefix-list is not required for tracking itself.
The 'ip sla schedule' is needed to start the operation, but the question asks for steps to use it for tracking, so the tracking object and its reference are key.
A network engineer configures IP SLA tracking for a static route on a Cisco router. The IP SLA operation is configured with a threshold of 100 ms and a timeout of 5000 ms. The tracked object is configured with a delay of 5 seconds for both up and down transitions. The engineer notices that when the remote host becomes unreachable, the static route is not removed from the routing table immediately. Which is the most likely explanation?
The delay down command in the tracked object introduces a hold-down period before the object state changes, so the route remains for that duration.
Why this answer
The IP SLA tracking delay configuration introduces a delay before the tracked object changes state; this is designed to prevent route flapping but can cause the static route to remain in the routing table for the configured delay period after the IP SLA operation fails.
What is the default threshold value (in milliseconds) for an IP SLA operation?
Correct. The default threshold is 5000 ms, same as the default timeout.
Why this answer
The default threshold for an IP SLA operation is 5000 milliseconds (5 seconds). This is the value above which the operation is considered to have exceeded a tolerable delay, triggering reaction conditions.
A network engineer configured IP SLA 30 to monitor the reachability of a server (10.10.10.10) using ICMP echo probes. The IP SLA is linked to a track object that is used in a static default route. The engineer notices that the IP SLA state is 'Active', but the static route is not present in the routing table. The track object shows 'Up'. What should the engineer check first?
The static route must be configured with 'ip route 0.0.0.0 0.0.0.0 <next-hop> track <track-number>'. If missing or wrong track number, the route will not be installed.
Why this answer
If the track object is up and the static route is not installed, the issue is likely that the static route configuration does not properly reference the track object, or the route is being overridden by another route with lower administrative distance.
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?
When BFD is used, the track is ignored for BGP session reset, but the track might still be up, so the static route associated with the track is not removed, causing the backup route to not be used.
Why this answer
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.
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?
The return code 'OK' and zero failures confirm successful operation.
Why this answer
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.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 6 Round Trip Time (RTT) for Index 6 Latest RTT: 0 ms Latest RTT (milliseconds): 0 Latest RTT (microseconds): 0 Number of successes: 0 Number of failures: 100 Operation time to live: Forever Output: No connection R1# show track 4 Track 4 IP SLA 6 reachability Reachability is Down 3 changes, last change 00:05:00 Latest operation return code: No connection Latest RTT (milliseconds): 0 Tracked by: ip route 0.0.0.0 0.0.0.0 192.168.4.1 track 4 R1# show ip route 0.0.0.0 0.0.0.0 % Network not in table Based on this output, which statement is correct?
The 'No connection' indicates unreachability, and the track down removes the static route.
Why this answer
The track is down due to 'No connection', and the static route is not in the routing table. This indicates that the IP SLA probe cannot reach the target, and the tracked route has been removed.
Which TWO statements about IP SLA ICMP echo operations are true? (Choose TWO.)
The ICMP echo operation sends ICMP packets and calculates the RTT based on the reply.
Why this answer
IP SLA ICMP echo measures round-trip time (RTT) by sending ICMP echo requests and waiting for replies. It does not measure jitter (that requires UDP jitter operations). It can be configured with a frequency and a timeout, and the operation must be started with the 'ip sla schedule' command.
The source IP can be specified, but the destination must be an IP address, not a hostname unless DNS resolution is configured.
A network engineer configures IP SLA with an ICMP echo operation to monitor a remote host. The engineer also configures a route map to set the next hop based on the IP SLA track object. The engineer notices that the route map is not applied to the routing table as expected. The show ip route shows the static route with the correct next hop, but the route map does not seem to affect the routing decision. Which is the most likely explanation?
To use a route map with a static route, the route map must be referenced in the static route configuration; otherwise, it has no effect.
Why this answer
Route maps can be used with IP SLA tracking to modify route attributes, but the route map must be applied to the routing process or to the static route itself. If the route map is configured but not applied correctly, it will not affect the routing table. Additionally, route maps used with IP SLA tracking are typically applied to redistribution, not to static routes directly.
The most common edge case is that the route map is not applied to the static route using the 'route-map' keyword under the 'ip route' command.
Which IP SLA operation type is used to monitor the availability of a TCP-based service by attempting a three-way handshake?
Correct. TCP Connect performs a TCP three-way handshake to test service availability.
Why this answer
The TCP Connect operation (type 5) attempts to establish a TCP connection to a specified port. Success indicates the service is reachable; failure indicates a problem.
Given the following partial configuration on router R1: ip sla 10 icmp-echo 192.168.1.1 source-ip 10.0.0.1 frequency 10 ip sla schedule 10 life forever start-time now Which statement best describes the effect of this configuration?
The icmp-echo command defines the destination, source-ip sets the source, and frequency sets the interval.
Why this answer
The configuration creates an IP SLA operation that sends ICMP echo probes to 192.168.1.1 every 10 seconds, using source IP 10.0.0.1. The schedule starts immediately and runs indefinitely.
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?
The configuration shows 'icmp-echo' type, target 192.168.1.1, and frequency 60 seconds.
Why this answer
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.
Drag and drop the steps to verify and validate IP SLA operational state into the correct order, from first to last.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Why this order
Begin by checking the overall IP SLA configuration to confirm the operation is defined, then review the latest statistics for RTT and success rate, examine the reaction configuration if tracking is used, verify the tracking object status, and finally confirm that tracked objects are influencing routing or policy.
A network engineer runs the following command to troubleshoot an IP SLA issue: R1# debug ip sla monitor trace IP SLAs Monitor trace debugging is on *Mar 1 12:34:56.789: IP SLAs Monitor: Starting operation 10 *Mar 1 12:34:56.789: IP SLAs Monitor: Sending ICMP echo request to 192.168.1.1 *Mar 1 12:34:56.790: IP SLAs Monitor: Received ICMP echo reply from 192.168.1.1 *Mar 1 12:34:56.790: IP SLAs Monitor: RTT = 12 ms *Mar 1 12:34:56.790: IP SLAs Monitor: Operation 10 completed successfully *Mar 1 12:35:56.789: IP SLAs Monitor: Starting operation 10 *Mar 1 12:35:56.789: IP SLAs Monitor: Sending ICMP echo request to 192.168.1.1 *Mar 1 12:35:56.790: IP SLAs Monitor: Received ICMP echo reply from 192.168.1.1 *Mar 1 12:35:56.790: IP SLAs Monitor: RTT = 14 ms *Mar 1 12:35:56.790: IP SLAs Monitor: Operation 10 completed successfully What does this output indicate?
Each cycle shows request, reply, and 'completed successfully'.
Why this answer
This debug output shows the IP SLA monitor trace for operation 10. Each cycle shows a successful ICMP echo request/reply with RTT values, indicating the probe is working correctly.
An engineer configured IP SLA 60 to monitor the reachability of a WAN link's next-hop (203.0.113.1) using ICMP echo. The IP SLA is used in a track object for a floating static route. The engineer notices that the primary route (EIGRP) is present, but the floating static route is not installed when the primary fails. The track object shows 'Down' after the primary fails. What should the engineer check?
If the static route has an AD lower than EIGRP (e.g., 1), it would be installed even when the primary is up, causing issues. For a floating static, AD must be higher.
Why this answer
A floating static route with tracking requires the administrative distance to be higher than the primary route. If the AD is lower or equal, the static route will not be installed as a backup. Also, the track object must be correctly referenced.
Drag and drop the steps to configure and schedule an IP SLA ICMP-echo operation into the correct order, from first to last.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Why this order
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.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 5 Round Trip Time (RTT) for Index 5 Latest RTT: 50 ms Latest RTT (milliseconds): 50 Latest RTT (microseconds): 50000 Number of successes: 100 Number of failures: 0 Operation time to live: Forever Output: OK R1# show track 3 Track 3 IP SLA 5 reachability Reachability is Up 1 change, last change 00:10:00 Latest operation return code: OK Latest RTT (milliseconds): 50 Tracked by: ip route 0.0.0.0 0.0.0.0 192.168.3.1 track 3 R1# show ip route 0.0.0.0 0.0.0.0 Routing entry for 0.0.0.0/0, supernet Known via "static", distance 1, metric 0, candidate default path Last update from 192.168.3.1 on GigabitEthernet0/0 Routing Descriptor Blocks: * 192.168.3.1, via GigabitEthernet0/0 Route metric is 0, traffic share count is 1 Based on this output, which statement is correct?
The routing table shows the static route is installed with next-hop 192.168.3.1, and the track confirms reachability.
Why this answer
The track is up, and the static route is present in the routing table. The IP SLA has 100% success. This indicates everything is working correctly.
What is the default frequency (in seconds) for an IP SLA operation if not explicitly configured?
The default frequency is 60 seconds.
Why this answer
The default frequency for IP SLA operations is 60 seconds. This means probes are sent every 60 seconds unless overridden with the frequency command.
An engineer configured IP SLA 20 to monitor the reachability of a next-hop router (192.168.1.1) using UDP jitter probes. The goal is to use the IP SLA with a track object to influence EIGRP route selection. However, the EIGRP route is not being affected by the IP SLA state. The engineer verifies that the IP SLA is 'Active' and the track object shows 'Up'. What is the most likely misconfiguration?
EIGRP does not have a mechanism to directly track IP SLA states. The engineer must use a tracked static route or policy-based routing to influence traffic.
Why this answer
EIGRP does not natively react to IP SLA track objects unless the route is redistributed or a static route with tracking is used. The engineer likely expected EIGRP to automatically adjust metric based on IP SLA, which is not supported.
Which IP SLA operation type is used to measure one-way delay, jitter, and packet loss?
udp-jitter is designed to measure delay, jitter, and packet loss.
Why this answer
The udp-jitter operation type measures one-way delay, jitter, and packet loss by sending a stream of UDP packets and analyzing the responses.
Which THREE symptoms indicate that an IP SLA operation is failing or not responding? (Choose THREE.)
A timeout indicates that the probe did not receive a reply within the configured timeout.
Why this answer
When an IP SLA operation fails, the 'show ip sla statistics' output will show 'Timeout' or 'No connection' in the latest RTT field. The return code in the detailed output will be non-zero (e.g., 1 for timeout). The tracking object will show 'Down' if it is configured to track reachability.
A zero RTT value is not typical for a failure; it might indicate a misconfiguration. The operation state 'Active' means it is running, not failing.
What is the default inter-packet interval (in milliseconds) for an IP SLA UDP Jitter operation?
Correct. The default inter-packet interval is 20 ms.
Why this answer
The default inter-packet interval for UDP Jitter is 20 milliseconds. This is the delay between sending successive packets within a single probe.
Which TWO commands are used to configure an IP SLA ICMP echo operation on a Cisco IOS device? (Choose TWO.)
This command enters IP SLA configuration mode for operation number 1.
Why this answer
To configure an IP SLA ICMP echo operation, you start with 'ip sla <operation-number>' to enter IP SLA configuration mode, then use 'icmp-echo <destination> [source-ip <src>]' to define the probe. The 'frequency' command sets how often the probe is sent. The 'ip sla schedule' is used to start the operation, not to configure it.
The 'track' command is used separately to monitor the operation. The 'ip sla monitor' is legacy.
An enterprise uses IP SLA to track a route to a remote site via two ISPs. Router R1 has: ip sla 3 icmp-echo 8.8.8.8 source-ip 10.0.0.1 frequency 10 ip sla schedule 3 life forever start-time now track 3 ip sla 3 reachability ip route 10.10.10.0 255.255.255.0 10.0.0.2 track 3 ip route 10.10.10.0 255.255.255.0 10.0.1.2 10 When the primary ISP fails, the backup route is used, but traffic to 10.10.10.0/24 is intermittently lost. Show output on R1: show ip route 10.10.10.0 Routing entry for 10.10.10.0/24 Known via "static", distance 1, metric 0 Last update from 10.0.0.2 on GigabitEthernet0/0 * 10.0.1.2, via GigabitEthernet0/1 What is the root cause?
The track monitors reachability to 8.8.8.8, not the next-hop. If the backup path can reach 8.8.8.8, the track stays up, and the primary route remains installed even though the next-hop is unreachable.
Why this answer
The tracked route is still present in the routing table even though the track is down. This happens because the track is only removed if the track state is 'down', but the show output shows the route is still there. The likely cause is that the track is not properly associated with the route, or the route has a higher administrative distance that is not being overridden.
However, the correct answer is that the track 3 is configured with 'reachability' but the IP SLA probe may be successful due to a different path, so the track remains up, but the primary next-hop is actually unreachable, causing packet loss.
Consider this IP SLA configuration on router R6: ip sla 60 udp-echo 203.0.113.1 2000 source-ip 198.51.100.1 frequency 20 ip sla schedule 60 life forever start-time now What is the purpose of this configuration?
UDP echo operation sends a UDP datagram and waits for a reply to measure round-trip time.
Why this answer
The configuration sends UDP packets to destination 203.0.113.1 on port 2000, sourced from 198.51.100.1, every 20 seconds. It tests UDP connectivity and response time.
A network engineer runs the following command on Router R1: R1# show ip sla configuration 1 IP SLAs Infrastructure Engine-II Entry number: 1 Owner: Tag: Type of operation to perform: icmp-echo Target address: 192.168.1.1 Source address: 0.0.0.0 Source interface: none Type Of Service parameter: 0 Verify data: No Operation timeout (milliseconds): 5000 Request size (ARR data block): 28 Threshold (milliseconds): 100 Frequency (seconds): 10 Life (seconds): Forever Ageout (seconds): 0 Based on this output, what is the primary problem with this IP SLA configuration?
A source address of 0.0.0.0 means the router uses the IP of the egress interface, but if that interface is down or has no IP, the probe may fail. This is a common misconfiguration.
Why this answer
The source address is 0.0.0.0 and no source interface is configured. This means the router will use the outgoing interface's IP address, which might not be routable or expected. However, the key clue is that the threshold is set to 100 ms, but the operation timeout is 5000 ms.
If the RTT exceeds 100 ms, the operation will report 'Over threshold' but not necessarily fail. The question focuses on configuration issues; the source address being 0.0.0.0 is a common misconfiguration that can cause problems if the router cannot reach the target.
An engineer configures IP SLA with an ICMP echo operation and tracks it with a static route. The IP SLA operation is configured with a source interface of Loopback0. The engineer notices that when the remote host becomes unreachable, the static route is removed, but when the remote host becomes reachable again, the static route is not reinstalled immediately. The show ip sla statistics shows the operation is 'Active' and 'Success'. Which is the most likely explanation?
The delay up command in the track object introduces a hold-down period before the object state changes to up, so the route is not reinstalled immediately.
Why this answer
When an IP SLA operation uses a source interface, the operation may fail if that interface is down, but more importantly, the track object may have a delay configured for up transitions. Additionally, the static route may have a higher administrative distance that prevents it from being reinstalled if another route to the same prefix exists. However, the most common edge case is that the track object has a 'delay up' configured, which delays the route installation after the operation recovers.
An engineer configures IP SLA with an ICMP echo operation to track a remote host, but the IP SLA responder is not configured on the remote router. The IP SLA operation shows 'Timeout' in the show ip sla statistics output. The engineer expects the operation to succeed because the remote host is reachable via ping. Which is the most likely explanation?
IP SLA ICMP echo uses a specific protocol format that differs from standard ping; the responder is needed for proper operation.
Why this answer
IP SLA ICMP echo operations require the IP SLA responder to be enabled on the remote device for accurate round-trip time measurement; without it, the operation may still work but can time out due to packet processing differences, or the operation may fail entirely if the remote device does not respond to ICMP echo requests in a timely manner as per IP SLA expectations.
Which IP SLA operation type uses ICMP Echo Request/Reply packets to measure round-trip time?
Correct. ICMP Echo is the IP SLA operation that uses ICMP Echo Request/Reply.
Why this answer
The IP SLA ICMP Echo operation (type 1) uses ICMP Echo Request and Echo Reply messages to measure network latency and availability.
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 192.168.1.1 RTT=50ms OK 1s ago 2 icmp-echo 192.168.1.2 RTT=2000ms Over threshold 2s ago 3 icmp-echo 192.168.1.3 RTT=100ms OK 3s ago Based on this output, which statement is correct?
The return code 'Over threshold' directly indicates that the RTT exceeded the threshold, implying high latency.
Why this answer
The 'Return Code' column shows 'Over threshold' for ID 2, meaning the RTT exceeded the configured threshold. The other operations are OK. This output does not indicate failure or timeout unless the return code says so.
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?
The low standard deviation and 'Over thresholds occurred: FALSE' confirm stability.
Why this answer
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.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 2 Round Trip Time (RTT) for Index 2 Latest RTT: No connection Latest RTT (milliseconds): No connection Latest RTT (microseconds): No connection Number of successes: 0 Number of failures: 100 Operation time to live: Forever Output: No connection Based on this output, which statement is correct?
'No connection' indicates that the probe failed to reach the target, likely due to unreachability or lack of response.
Why this answer
The output shows 'No connection' for RTT and 'Output: No connection'. This indicates that the IP SLA operation cannot reach the target. The 100 failures confirm this.
This is a clear sign of a connectivity issue.
What is the default number of packets sent per IP SLA UDP Jitter operation?
Correct. The default is 10 packets per operation.
Why this answer
The default number of packets per UDP Jitter operation is 10. This is the number of UDP packets sent in each probe interval to measure jitter and packet loss.
A company uses IP SLA to track a route to a remote network via a DMVPN tunnel. Router R1 (hub) has: ip sla 5 icmp-echo 172.16.0.1 source-ip 10.0.0.1 frequency 10 ip sla schedule 5 life forever start-time now track 5 ip sla 5 reachability ip route 192.168.1.0 255.255.255.0 Tunnel0 track 5 Tunnel0 is a DMVPN tunnel to spoke R2. The tunnel is up, but the route is intermittently removed. Show output on R1: show ip route 192.168.1.0 % Subnet not in table show track 5 Track 5 IP SLA 5 reachability Reachability is Down 2 changes, last change 00:00:05 What is the root cause?
The probe should be sourced from the tunnel source IP to ensure it goes through the tunnel; otherwise, it may be dropped or not reach the target.
Why this answer
The IP SLA probe is sent to 172.16.0.1, which is the tunnel IP of R2. However, the DMVPN tunnel might be using a different encapsulation (e.g., mGRE) and the probe might be sent over the physical interface instead of the tunnel, or the tunnel might be in a VRF. The correct answer is that the IP SLA probe is sourced from 10.0.0.1, which is not the tunnel source, so the probe goes out the physical interface and may not reach 172.16.0.1, causing the track to go down.
An engineer configures IP SLA to track a route to a server in a VRF. Router R1 has: ip sla 6 icmp-echo 10.10.10.10 source-ip 192.168.1.1 frequency 10 ip sla schedule 6 life forever start-time now track 6 ip sla 6 reachability ip route vrf BLUE 0.0.0.0 0.0.0.0 192.168.1.2 track 6 But the route is never installed in the VRF routing table. Show output: show ip route vrf BLUE | include 0.0.0.0 % No default route found What is the root cause?
The IP SLA must be configured with 'vrf BLUE' to send probes within the VRF; otherwise, the track will not work correctly.
Why this answer
The IP SLA probe is not VRF-aware. By default, IP SLA operates in the global routing table. To track a route in a VRF, the IP SLA must be configured with the vrf keyword.
The correct answer is that the IP SLA is not associated with the VRF, so the probe fails or is sent in the wrong context.
An engineer configures IP SLA with an ICMP echo operation and uses it to track a static default route. The engineer also configures a backup static route with a higher administrative distance. The IP SLA operation is configured with a timeout of 2000 ms and a frequency of 5 seconds. The engineer notices that when the primary route is removed due to IP SLA failure, the backup route is installed, but when the IP SLA operation recovers, the primary route is not reinstalled. The show ip route shows the backup route still present. Which is the most likely explanation?
The delay up command in the track object introduces a hold-down period before the object state changes to up, so the primary route is not reinstalled immediately.
Why this answer
When a tracked static route is removed, the backup route with higher AD is installed. When the IP SLA operation recovers, the track object goes up, and the primary route should be reinstalled. However, if the IP SLA operation recovers but the track object has a delay up configured, or if the primary route's AD is not lower than the backup route, the primary route may not be reinstalled.
In this scenario, the most likely edge case is that the track object has a 'delay up' configured, which delays the route installation.
A network engineer is troubleshooting a site-to-site VPN that intermittently drops. The engineer configured IP SLA 10 to track reachability of the remote LAN gateway (10.1.2.1) using ICMP echo probes every 5 seconds. The IP SLA is used in a static route to influence failover. The engineer notices that the IP SLA state shows 'Active' but the tracked route is not installed. What is the most likely cause?
If the track object is not properly linked (e.g., 'track 1 ip sla 10 reachability' missing), or the static route uses a different track number, the route will not be installed even though the IP SLA is active.
Why this answer
The IP SLA is active, but the tracked object might not be configured correctly to react to the IP SLA state. The issue is that the track object is not linked to the IP SLA or the threshold is misconfigured.
Drag and drop the steps to troubleshoot IP SLA adjacency or connectivity failures into the correct order, from first to last.
Drag steps to the numbered slots on the right, or tap a step then tap a slot.
Why this order
Start by verifying the IP SLA operation state to see if it is active or failed, then check reachability to the target using extended ping with the same source, inspect the IP SLA configuration for errors, review access lists or routing that may block probes, and finally adjust parameters like threshold or timeout as needed.
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?
Each entry shows 'Return Code = OK' and RTT between 11-14 ms.
Why this answer
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.
Which TWO statements about IP SLA reaction configuration and event monitoring are true? (Choose TWO.)
Correct. Using 'reaction-configuration' with 'react timeout' and 'action trapOnly' will generate a syslog trap on timeout.
Why this answer
The 'reaction-configuration' command allows specifying a type (e.g., timeout, threshold) and an action (e.g., trapOnly, trigger). The 'react' keyword defines the condition to monitor, such as 'connectionLoss' or 'timeout'. The 'action' keyword defines what happens when the condition is met.
The default action is 'trapOnly', meaning only a syslog trap is generated. The 'reaction-configuration' does not support 'react rtt' with 'action trigger' directly; instead, 'react rtt' uses threshold-based triggers.
Which IP SLA operation type uses ICMP to discover the path (hops) between source and destination?
Correct. ICMP Path Echo discovers the path by incrementing TTL.
Why this answer
The ICMP Path Echo operation (type 10) uses ICMP Echo requests with increasing TTL values to trace the path from source to destination, similar to traceroute.
A network engineer configured IP SLA 90 to monitor a remote router's loopback (10.0.0.1) using ICMP echo. The IP SLA is linked to a track object that is used in a static route. The engineer notices that the IP SLA state is 'Active', but the static route is not installed. The track object shows 'Up'. The engineer checks the routing table and sees a different route to the same destination with a lower administrative distance. What should the engineer do to ensure the IP SLA-tracked route is used when the primary fails?
To install the tracked route, the primary route must be removed (e.g., by shutting down the interface or redistributing). The tracked route will then be installed.
Why this answer
If a route with a lower AD exists, the IP SLA-tracked route will not be installed unless the primary route is removed. The engineer must ensure the tracked route has a higher AD than the primary route, or remove the primary route.
A network engineer configured IP SLA to track a BGP next-hop for a backup path. Router R1 has: ip sla 2 icmp-echo 192.168.2.2 source-ip 192.168.1.1 frequency 5 ip sla schedule 2 life forever start-time now track 2 ip sla 2 reachability router bgp 65001 bgp log-neighbor-changes neighbor 192.168.2.2 remote-as 65002 neighbor 192.168.2.2 fall-over bfd neighbor 192.168.2.2 track 2 However, when the link to 192.168.2.2 goes down, the BGP session does not reset immediately. What is the root cause?
When both fall-over bfd and track are configured, BFD is used first. If BFD is not established, the track may not be used, causing the session to stay up.
Why this answer
The BGP fall-over bfd command overrides the track 2 behavior. BFD provides faster detection, but if BFD is not configured on the neighbor or if the BFD session is not established, the track might not take effect. The correct answer is that the track 2 is ignored because BGP fall-over bfd takes precedence, and BFD is not actually operational.
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?
These operations are listed as 'Enabled'.
An engineer configures IP SLA with an ICMP echo operation and uses it to track a static route. The engineer also configures a backup static route with a higher administrative distance. The engineer notices that when the primary route is removed due to IP SLA failure, the backup route is installed, but when the IP SLA operation recovers, the primary route is not reinstalled. The show ip sla statistics shows the operation is 'Active' and 'Success'. The show track shows the track object is 'Up'. Which is the most likely explanation?
If the primary route has a higher AD, it will not be installed even when the track object is up, because the backup route is preferred.
Why this answer
When a tracked static route is removed and the backup route is installed, the primary route may not be reinstalled if the primary route's administrative distance is not lower than the backup route. However, in this scenario, the track object is up, so the primary route should be reinstalled. The most likely edge case is that the primary static route has a higher administrative distance than the backup route, which would prevent it from being reinstalled even when the track object is up.
This can happen if the engineer misconfigured the AD values.
Consider this IP SLA configuration on router R3: ip sla 30 icmp-echo 192.168.2.1 frequency 5 ip sla schedule 30 life forever start-time now What is missing from this configuration?
Without source-ip, the router defaults to the interface IP used for the route to the destination.
Why this answer
The configuration lacks a source IP address. While optional, without a source-ip, the router uses the outgoing interface IP, which may not be desired for tracking specific paths.
What is the default frequency (in seconds) for an IP SLA operation when no frequency is explicitly configured?
Correct. The default frequency for IP SLA operations is 60 seconds.
Why this answer
The default frequency for an IP SLA operation is 60 seconds. This means the probe is sent every 60 seconds unless a different frequency is configured under the IP SLA configuration.
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?
The IP SLA must be VRF-aware to send probes within the VRF; otherwise, the probe fails and the track goes down, but the route might still be installed due to other factors.
Why this answer
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.
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?
GRE adds overhead, and if the path MTU is not adjusted, ICMP packets may be dropped due to fragmentation, causing the track to flap.
Why this answer
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.
Which TWO statements correctly describe the behavior of IP SLA with the 'threshold' and 'timeout' configuration? (Choose TWO.)
Correct. The threshold is the value that triggers a reaction event; it must be lower than the timeout to allow the reaction to occur before the operation times out.
Why this answer
The 'threshold' command sets the rising threshold for reaction triggering, while 'timeout' specifies how long the probe waits for a response before marking the operation as a failure. The timeout must be less than the frequency interval; otherwise, the probe may overlap. The default timeout is 5000 ms, not 10000 ms.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 7 Round Trip Time (RTT) for Index 7 Latest RTT: 500 ms Latest RTT (milliseconds): 500 Latest RTT (microseconds): 500000 Number of successes: 30 Number of failures: 70 Operation time to live: Forever Output: Over threshold R1# show track 5 Track 5 IP SLA 7 reachability Reachability is Up 1 change, last change 00:20:00 Latest operation return code: Over threshold Latest RTT (milliseconds): 500 Tracked by: ip route 0.0.0.0 0.0.0.0 192.168.5.1 track 5 Based on this output, which statement is correct?
The track is up, meaning the failure rate is within the acceptable range defined in the track configuration.
Why this answer
The track is up despite the 'Over threshold' return code. This can happen if the track is configured to use a different threshold for reachability (e.g., based on number of consecutive successes or a different percentage). The IP SLA has 30 successes and 70 failures, but the track still considers it up, likely because the threshold for down is higher (e.g., 100% failures).
An engineer configures IP SLA to track a route to a loopback address for BGP next-hop tracking. Router R1 has: ip sla 4 icmp-echo 192.168.100.1 source-ip 10.0.0.1 frequency 5 ip sla schedule 4 life forever start-time now track 4 ip sla 4 reachability router bgp 65001 neighbor 10.0.0.2 remote-as 65002 neighbor 10.0.0.2 update-source Loopback0 neighbor 10.0.0.2 ebgp-multihop 2 neighbor 10.0.0.2 fall-over bfd But the BGP session to 10.0.0.2 is flapping every 5 seconds. What is the root cause?
CoPP might rate-limit ICMP packets, causing the BFD session to fail if BFD relies on the same path and the router's CPU is overwhelmed.
Why this answer
The IP SLA probe is sent to 192.168.100.1, but the BGP neighbor is 10.0.0.2. The track is not directly affecting the BGP session. However, the flapping is caused by the BFD session failing because the IP SLA might be interfering with the BFD packets, or more likely, the ebgp-multihop and BFD interaction.
The correct answer is that the BFD session is using the same path as the IP SLA, and the IP SLA probe is causing the BFD session to reset due to packet loss or delay.
A network engineer configured IP SLA 70 to monitor a remote site's LAN gateway (172.16.1.1) using ICMP echo. The IP SLA is linked to a track object that is used in a static route for a backup link. The engineer notices that the IP SLA state is 'Active', but the backup static route is installed in the routing table even when the primary route is available. What is the most likely cause?
Without the 'track' keyword, the static route is permanent and will be installed if its AD is lower than the primary route.
Why this answer
If the backup static route is installed while the primary route is available, the static route likely has a lower administrative distance than the primary route, or the track object is not being used correctly (e.g., the static route does not have the 'track' keyword).
An engineer configured IP SLA 80 to monitor a remote server (192.168.100.100) using ICMP echo. The IP SLA is used in a track object for a static route. The engineer notices that the IP SLA state is 'Active', but the track object shows 'Down'. What is the most likely cause?
A 'delay up' timer forces the track to wait before transitioning to 'Up' after the IP SLA becomes 'Active'. This is a common cause of mismatch.
Why this answer
The track object can be configured with a threshold (e.g., 'threshold' or 'delay') that causes it to remain 'Down' even if the IP SLA is 'Active'. For example, if the track object has a 'delay up' timer, it will not transition to 'Up' immediately.
Given this IP SLA configuration on router R4: ip sla 40 icmp-echo 10.10.10.1 source-ip 172.16.1.1 frequency 15 ip sla schedule 40 life forever start-time now Which statement is true?
The source-ip must belong to a local interface for the probe to be sourced correctly.
Why this answer
The configuration sends ICMP echo probes from 172.16.1.1 to 10.10.10.1 every 15 seconds. The source IP is explicitly set.
A network engineer configured IP SLA 50 to monitor a remote router's loopback (5.5.5.5) using ICMP echo. The IP SLA is linked to a track object that is used in a PBR (policy-based routing) route-map. The engineer notices that the PBR is not applying the alternate path when the IP SLA goes down. The track object shows 'Down'. What is the most likely misconfiguration?
Without 'verify-availability', PBR does not check the track state and will continue using the primary next-hop even if the track is down.
Why this answer
PBR with set ip next-hop verify-availability requires the track object to be referenced correctly in the route-map. If the route-map uses 'set ip next-hop verify-availability' but does not include the track keyword, PBR will not react to the IP SLA state.
A network engineer runs the following command to troubleshoot an IP SLA issue: R1# debug ip sla trace IP SLAs trace debugging is on *Mar 1 12:34:56.789: IP SLAs: Starting operation 10 *Mar 1 12:34:56.789: IP SLAs: Sending ICMP echo request to 192.168.1.1 *Mar 1 12:34:56.790: IP SLAs: Received ICMP echo reply from 192.168.1.1 *Mar 1 12:34:56.790: IP SLAs: RTT = 12 ms *Mar 1 12:34:56.790: IP SLAs: Operation 10 completed successfully *Mar 1 12:35:56.789: IP SLAs: Starting operation 10 *Mar 1 12:35:56.789: IP SLAs: Sending ICMP echo request to 192.168.1.1 *Mar 1 12:35:56.790: IP SLAs: Received ICMP echo reply from 192.168.1.1 *Mar 1 12:35:56.790: IP SLAs: RTT = 14 ms *Mar 1 12:35:56.790: IP SLAs: Operation 10 completed successfully What does this output indicate?
Each cycle shows 'completed successfully'.
Why this answer
This debug output shows the IP SLA trace for operation 10 (newer command). It confirms successful ICMP echo probes with RTT values, indicating the operation is functioning correctly.
What is the default timeout value (in milliseconds) for an IP SLA operation?
Correct. The default timeout is 5000 ms (5 seconds).
Why this answer
The default timeout for an IP SLA operation is 5000 milliseconds (5 seconds). If a response is not received within this time, the probe is considered failed.
Examine this IP SLA configuration on router R5: ip sla 50 icmp-echo 10.20.20.1 source-ip 192.168.10.1 frequency 10 ip sla schedule 50 life forever start-time now What is the effect of this configuration?
This is the standard behavior of icmp-echo IP SLA.
Why this answer
The configuration creates an IP SLA operation that sends ICMP echo probes to 10.20.20.1 every 10 seconds, using source IP 192.168.10.1. It starts immediately and runs forever.
A network engineer runs the following command on Router R1: R1# show ip sla statistics 1 Round Trip Time (RTT) for Index 1 Latest RTT: 200 ms Latest RTT (milliseconds): 200 Latest RTT (microseconds): 200000 Number of successes: 50 Number of failures: 10 Operation time to live: Forever Output: Over threshold Based on this output, which statement is correct?
'Output: Over threshold' directly means the measured RTT was above the threshold set in the IP SLA configuration.
Why this answer
The 'Output: Over threshold' line indicates that the latest RTT exceeded the configured threshold. The number of failures (10) suggests some probes failed, but the key clue is the threshold violation. This does not necessarily mean the operation is down; it means a threshold event occurred.
Examine this IP SLA configuration on router R2: ip sla 20 udp-jitter 203.0.113.10 16384 source-ip 198.51.100.1 source-port 16384 frequency 30 ip sla schedule 20 life forever start-time now Which statement is true?
UDP jitter operation measures delay, jitter, and packet loss.
Why this answer
The configuration measures UDP jitter by sending UDP packets to destination 203.0.113.10 on port 16384, sourced from 198.51.100.1 with source port 16384, every 30 seconds.
A network engineer runs the following command to troubleshoot an IP SLA issue: R1# show ip sla monitor 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?
Zero failures and 'OK' return code confirm success.
Why this answer
This output is from the older 'ip sla monitor' command, which is equivalent to 'ip sla'. It shows the same statistics: 100 successes, 0 failures, and a return code of OK, indicating the probe is working.
A large enterprise network is experiencing intermittent reachability to a critical server (10.10.10.10). Router R1 has the following relevant configuration: ip sla 1 icmp-echo 10.10.10.10 source-ip 192.168.1.1 frequency 10 ip sla schedule 1 life forever start-time now track 1 ip sla 1 reachability delay down 5 up 5 ip route 0.0.0.0 0.0.0.0 192.168.1.2 track 1 Router R2 (the next-hop) shows: show ip route | include 10.10.10.10 S 10.10.10.0/24 [1/0] via 10.0.0.1 What is the root cause?
The source IP 192.168.1.1 may not be in the routing table of the server or intermediate routers, so echo replies never return, causing the track to go down.
Why this answer
The IP SLA probes are sourced from 192.168.1.1, but the server 10.10.10.10 is in a different subnet. The return path from the server might not reach 192.168.1.1 due to route summarization or asymmetric routing. However, the key issue is that the tracked default route is removed when the probe fails, but the probe failure could be due to the server's response not being routed back correctly, not because the next-hop is unreachable.
The correct answer is that the source IP of the probe is not routable from the server's perspective, causing false negatives.
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