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VMWare - Cisco 3560 Problem

Hi,

VMWare slow ping responce

We are running 3 servers on single Dell hardware server. And this server is connected to 3560 swicth. But we find that there is a delay in responce time in this VMware server.

Responce time varies from 1 ms to about 200 ms erratically.

Can this be due to network problem?

Is it not possible that on a single hardware if three servers are running it will definiely delay the ping resonce time.

Can the switch responcibility be attributed only upto ping responce?

If "ping is less that 50 ms does that mean network is ok" how correct is this statement?

Please share the experinece.

any link on cisco.com is appreciable.

Thanks in advance

Subodh

6 REPLIES
Cisco Employee

Re: VMWare - Cisco 3560 Problem

Hello Subodh,

Verifying network performance using PINGs can be very misleading. Operating systems usually delay answering to ping packets to a certain amount of time, mostly if they are busy. Thus, you should correctly only compare pings to the same machine, not pings in general.

Unfortunately, the ping is by far too unreliable to pinpoint the cause of a problem - or to even indicate that there is a problem in the first place. Do you also ecounter other, different connectivity problems with the VMWare machines, or are this slow pings the only indication of a supposed problem?

Best regards,

Peter

Cisco Employee

Re: VMWare - Cisco 3560 Problem

Why don't you verify the ping outside of the VMWare to the same 3560? Such as the console of ESX or the host OS.

Regards,

jerry

Cisco Employee

Re: VMWare - Cisco 3560 Problem

Hello Jerry,

Nice to meet you here again. I was basically thinking about the same - pinging the host machine but I was aware of the fact that it would be an experiment under different conditions. If the pings remain erratic then it might be an indication of a deeper problem but if the pings will be nice and uniform, does that in any way move the issue further?

I think that the erratic pings alone are somewhat disconcerting but this requires more information and more symptoms to pinpoint what is going on - and whether there is something going on at all. With virtual machines, I tend to neglect similar nuances ;)

Best regards,

Peter

Cisco Employee

Re: VMWare - Cisco 3560 Problem

Hi Peter,

The reason I said to ping the host machine is I've seen issues when moving files across the network from VM. If the ping to the host machine is not consistent or with a high delay value, I would suggest to investigate the network (possible hardware also).

Regards,

jerry

Re: VMWare - Cisco 3560 Problem

Configure IP SLA on your switch, so then you can monitor your ICMP performances between your switch and your server

New Member

Re: VMWare - Cisco 3560 Problem

hi,

Thanks for your replay. ping responce varies erratically. And file copying is taking just too much time. we recently upgraded from 100 mbps switches to 3560 gigabit switches. Expecting speed should increase but in contrast access time has been increased. But ping responce is most of the times good <50 ms. Ideally it should be <1 ms. How can find out why there is so much delay even though we have new gigabit switches. All the interfaces are connected at 1000 mbps.

There are no input errors and no CRC.

Maximun link utilization is Rx 3/255 amd Tx 2/255. And queues of pending packets on any of the interfaces.

One thing I noticed that cpu utilization of the switch is 22 %. But earlier I had put this doubt on forum and got one link from cisco.com that states that cpu utilization can even be upto 50 % with minimum load.

Second thing i found out that out of many 3560 switches one switch is running PVST and all other are running IEEE STP ( that is default ). can this be the bottle neck ? .

Is there any way to find out why full network is so slow. Printing files on networks is taking redicuiously longer time.

Please share the experience to find the delay or to make sure that there is not problem from cisco network side. Can STP or any subnet duplication clashing cause such problem?

Can we find the how frames are travelling across the network? Something to tracert.

Thanks in advance

Subodh

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