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We have two switches that are behaving strangely. When I ping them the responses alternate between high and low results:

C:\Users\paul>ping sw-linksys1 -t

Pinging sw-linksys1.sep.com [172.16.254.235] with 32 bytes of data:
Reply from 172.16.254.235: bytes=32 time=39ms TTL=64
Reply from 172.16.254.235: bytes=32 time=154ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=142ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=143ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=146ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=152ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=153ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64
Reply from 172.16.254.235: bytes=32 time=153ms TTL=64
Reply from 172.16.254.235: bytes=32 time=2ms TTL=64

Other switches in the network behave normally. I've rebooted the switches, but the behavior still is there with the ping. Any ideas on how to troubleshoot this?

Thanks!

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I would check the switch for errors on the port. –  dbasnett May 9 '10 at 13:47

2 Answers 2

Ping is really only good for testing 'is the system up'. The response time is a bit of a red herring. In some systems ICMP ping responses are given a low priority, and therefore it's not a problem if the response time varies. I've also seen someone worry about ping response times and it turned out to be an problem on his own PC, not the systems he was worried about.

If this is the only thing you're seeing, I'd not worry about it. If you're seeing other problems, then I'd look at those problems.

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Agreed. Ping is not a performance monitoring tool. –  dbasnett May 8 '10 at 22:29

Look on the switch for the word "Linksys". Just kidding (mostly). But try pinging something that is connected to the switch, rather than the switch itself. If that works normally, then it's probably something in the switch firmware, and that can vary from product to product. Who knows, maybe it goes and tries to start a webserver process for you, thinking that after the ping will come a connection request.

Watching the process through Wireshark can also reveal more information. For instance, before you can ping from one IP address to another, there is going to be an ARP exchange preceeding it. Maybe that's where the confusion is (not that that's any more revealing).

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