Network Lag

Hi, I started having an issue where when I am pinging vm servers and other network devices i am getting a lag in ping. the time fluctuates but this doesn't happen all the time. Sometimes during the day, sometimes at night.

Backups run at night.

I have a APC power strip and one of them is having the lag. Any ideas?

Thank you
AquaJ9Asked:
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jmcgOwnerCommented:
How large a lag are you seeing?

The processor in the APC device may be quite limited and it could just be slow to respond when it's doing a scheduled housekeeping task.
AquaJ9Author Commented:
The time just fluctuates and my monitoring software reports ping down throughout the day.

Im thinking maybe its something on the switches
Bill BachPresident and Btrieve GuruCommented:
Some lag is expected, especially to and from virtual machines, due to the nature of virtualization and the ability of the VM host to coalesce multiple NIC interrupts.  Since you didn't clarify the extent of the issue, it may just be that you have some latency issues, or it may be that the machines are busy (as responding to a PING is not exactly a high priority task).

Of course, PING is not the best tool, as it has limited resolution.  Kwakkelflap's FPING is a better idea.  A even better option would be to set up a laptop with a running copy of Wireshark.  Plug it into the switch next to a server and send a few PING packets.  Then, in Wireshark, check the DeltaTime from the outbound request to the reply.  This is a MUCH more accurate way to capture network latency time.  

Once you have the base latency at the core switch, move it one switch away and repeat.  Then move it another switch away and repeat.  Using this, you can build up a PING map from various ports on the network switches to one or more servers.  If you see that moving outward past a specific switch shows a delay, thenyou might have a very slow (or otherwise overloaded) switch.

Also, remember that latency times can vary throughout the day as network load changes.  An idle switch will have less latency that a very busy one.  Further, if you are hopping subnets, remember that you have to go through a router as well -- and this can be another choke point.

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AquaJ9Author Commented:
This is a very good point BillBach

I will test this this week.
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Network Analysis

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