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CCNA 7.2: Troubleshoot network connectivity issues using ICMP echo-based IP SLA

Overview:

The ICMP Echo operation measures end-to-end response time between a Cisco router and any devices using IP

Study Notes:

• The ICMP Echo operation measures end-to-end response time between a Cisco router and a device using IP
• ICMP Echo is useful for troubleshooting network connectivity issues
• An IP SLA (Service Level Agreement) is configured on the source router
• The ICMP echo-based IP SLA detects packet loss when no ICMP echo responses are received
• Response time is computed by measuring the time taken between sending an ICMP Echo request message to the destination and receiving an ICMP Echo reply
• Response time is round-trip time (RTT) regardless of the number of hops between source and destination
• The IP SLA source router sends an ICMP echo packet to a specific destination at the configured time and frequency
• The SLA may be configure with a timeout value, which specifies the amount of time the source will wait for a response from the destination
• The SLA may be configured with a threshold value, which is used to set the number of missed responses before the SLA is considered to be violated
• The SLA may be configured with history settings to specify how the statistics from previous ICMP responses are maintained
• The ICMP Echo operation can be displayed and analyzed to determine how the network IP connections are performing

Configuration

config t
  ip sla <operation-number>
  icmp-echo <destination-ip-address> source-ip <source-ip-address>
  history buckets-kept <size>
  history filter failures
  frequency <seconds>
  history hours-of-statistics-kept <hours>
  history lives-kept <lives>
  history statistics-distribution-interval <milliseconds>
  threshold <milliseconds>
  timeout <milliseconds>

Schedule the SLA

ip sla schedule 1 life forever start-time now

Troubleshooting Tips

• If the IP Service Level Agreements (SLAs) operation is not running and not generating statistics, add the verify-data command to the configuration (while configuring in IP SLA configuration mode) to enable data verification
• When data verification is enabled, each operation response is checked for corruption. Use the verify-data command with caution during normal operations because it generates unnecessary overhead
• Use the debug ip sla trace and debug ip sla error commands to help troubleshoot issues with a IP SLA operations

Links: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipsla/configuration/15-mt/sla-15-mt-book/sla_icmp_echo.html#GUID-03ECDB03-38A3-458B-9922-7E659548D754