IP SLA icmp-echo question

[mantis]

Hi, 

I have a question on the ip sla icmp-echo operation. If an icmp response that isn't an echo reply (like destination unreachable) is received, will this result in an ip  sla timeout  return code? 

Thanks

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[Flavio Miranda]

Destination unreacheable is an echo  reply somehow.

Ip sla consider sucess and no sucess 

[mantis]

Hi there, 

Thanks for the reply, 

icmp echo-reply is a specific response type code. This differs from the the other codes covering unreachable/prohibited etc.

Additionally, depending on the type these can be generated from a host in path rather than the destination host being targeted in the icmp-echo 

Are you saying that ANY icmp response is treated as a success for ip sla ? 

[Flavio Miranda · Accepted solution]

Not that.

What I said is that, you may have response or not and unreacheble is considered 'not response' and will be counted as timeout.

I build this simples Lab when all routers speaks with each other using OSPF.  From R4 to R5 I can ping successfully using loopback interface.

 IPSLA was showing  successes:

IPSLA operation id: 6
Type of operation: icmp-echo
Latest RTT: 48 milliseconds
Latest operation start time: *23:37:10.011 UTC Mon Apr 18 2022
Latest operation return code: OK
Number of successes: 2
Number of failures: 0
Operation time to live: Forever

Then, I went to R5 and I take the lookback interface off the OSPFprocess. This would cause ping unreachable on R4. 

Then, the IP SLA registered the event as timeout and increase the "Number of failures" to 1.

IPSLA operation id: 6
Type of operation: icmp-echo
Latest RTT: NoConnection/Busy/Timeout
Latest operation start time: *23:38:10.011 UTC Mon Apr 18 2022
Latest operation return code: Timeout
Number of successes: 2

Number of failures: 1
Operation time to live: Forever

[balaji.bandi]

IP SLA simple mechanism used to identify far the end is reachable or not in terms of reachability,

if the return code is OK then all is good, if the return code is anything else IP SLA treats as down, based on the action will be triggered.

[mantis]

Thanks for the clarification.

Very much appreciated with the effort (LAB setup) to confirm 

Thanks

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