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I have a question regarding detecting a physical link problem with ping.

If we have a fiber or cable which has a problem and generate some CRC errors on the frame (visible with switch or router interface statistics), it's possible all ping tests would succeed, because of the default small ICMP packet size and statistically fewer possibilities of error. Is this correct?

Also, if I ping, with a 65k packet size, one ping will generate approximately 65000 / 1500(MTU) = 43 frames or IP fragments, then the probability for packet loss would be higher. Normally if one IP fragment is lost the entire IP packet is lost. Is this assumption is true ?

The global question is, with large ping, could we detect a physical problem on a link?

Cory Knutson
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bdes31
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1 Answers1

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ping is a fast diagnostic method, useful to identify macroscopic network problems. For example, if one thousand intra-LAN pings show a 2% packet loss, than you have a significant problem.

Your observation about ping size is valid: bigger pings result in more network load/stress. Rather issuing bigger than MTU pings, however, I would increment their frequency (if using Linux, you can use ping -f to flood the destination host).

That said, ping is not the best, or more comprehensive, tool at your disposal. For in-depth testing, I would use netbench or iperf.

shodanshok
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