are there any IP SLA dest-port limitations

[alexneishell]

are there any IP SLA dest-port limitations that anyone is aware of, or has documentation for? If I have a large network, and want to test to a core location, are there any limitations on the responder if the probes are set to use the same UDP port? Is there a threshold where the measurement could/would be impacted?

Or, is this function considered to be part of the configurable IP SLA operations for the router?

thanks,

Alex

[Vinod Arya]

Though IP SLA need source port to be individual and unique else the operation may fail, but not sure of dest-port if has any restriction.

IP SLA does support the exact same destination port of the same destination adress in the responder. (e.g. you can configure 10 udp jitter operations in the sender router with the exact same destination address and same udp port#, and run them anytime).

IP SLA responder is designed to do so. You should configure IP SLA Responder on the destination device!

Just not sure of what is the limit.

-Thanks

Vinod

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[alexneishell]

Thanks Vinod - responder is definitely configured on far end of test (using udp-jitter). More to what I was getting at was in the case of a large network, lets say I have a large number of vlans that need performance information to a Core location. I don't have an exact number (yet) of how many probes I would need, but lets just say there are 300 pointing to the same UDP port on the responder. At what point do the probes become impacted? Documentation shows that the probes are very scalable, but I can't find anything that shows the impact on the responder if probes requests become too heavy.

[Vinod Arya]

That being IP SLA design question on IOS, I unfortunately don't have exact figures. Also, it is suggested as best practice to keep separate dest-ports as far as possible.

-Thanks

Vinod

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[syekhali]

Hi Alex,

You could configure destination port number in the range from 1 to 65535.

There is no mention of the available destination ports in the newer IOS IP SLA config guides

http://www.cisco.com/en/US/docs/ios-xml/ios/ipsla/configuration/15-mt/sla_udp_jitter.html#GUID-7E49ED89-D853-4DB5-B997-AF10B40E2C2F

However, the 12.4 IOS guide confirms the same:-

http://www.cisco.com/en/US/docs/ios/12_4/ip_sla/configuration/guide/hsjitter.html#wp1051884

Let me know if it is helpful and answers your query.

Regards,

Syed Khalid

[alexneishell]

thanks for the response Syed. I was really trying to see if there are any limitations on the responder. For instance, if I have 100 probes pointing to a single shadow router, using a single UDP port, are there any performance issues? So not the ports that are available for use, but rather how large implementations affect performance of the probes, especially if they are pointed to the same responder port.

[syekhali]

Hi Alex,

I believe it is something with your network policy that you need to use the same UDP port. If the opertions pointing to a single router are evenly spaced and still a single port is incorporated in the operations it should not have any implications but the network usage might incur some losses to the data you might be looking at as statistics.

I would recommend usage of  different port numbers if you are planning to implement like 100 probes. Else, you could evenly space the operations when you schedule them.

Let me know if the information provided is helpful.

Regards,

Syed Khalid

[alexneishell]

appreciate the responses everyone. I'll say this, if I reach a destination port limitation, I'll be sure to reopen this thread.

[alexneishell]

I did end up finding the following bug thaqt applies to my original question, so better to use different udp ports if you can

Crash/Tracebacks occurs with IP SLA Responder on ASR1002

CSCuh56327

Description

Symptom: IP SLA responder crash occurs on Cisco ASR 1002 router in Cisco IOS Release 15.2(4)S, Cisco IOS Release 15.2(4)S1, and Cisco IOS Release 15.2(4)S2.
Conditions:This symptom occurs when ip sla udp jitter with precision microseconds, udp jitter with milliseconds and udp echo are configured on the sender device with the same destination port on Cisco ASR 1002 router.
Workaround:Use different destination ports for udp-echo and udp jitter with millisecond precision than udp jitter with microsecond and optimize timestamp.