HIGH PING LATENCY TO VLAN GATEWAYS

[nizarkotakkal]

Hi,

I am getting high latency while pinging to VLAN gateways, which is created in core switch. The ping status to the client devices are normal (1ms).

The two core switches  are 4500 , which are in SSO redundancy mode  , connected by ether channels. And the core switch is the root of spanning tree. 

Please provide some solution for this issue.

[devils_advocate]

Generally pinging the management address of switch is not a reliable method to test for latency.

My understanding is that the CPU of the switch has to handle the ICMP packet and it will not prioritise these over other traffic so the reply you get will generally be slower than if you were trying to ping from host to host on the LAN,

When pinging from host to host, the frames are forwarded in hardware by the switch so there is no delay.

If it were me, I would check the utilisation on the switch to ensure its nothing is running higher than expected and if your host to host RTT's are ok then I would be satisfied. 

[nizarkotakkal]

@ devils_advocate

    Thank you very much for your information.

• When pinging from host to access switches also giving normal result 1ms .
• Even in off-hours also the ping to core switch is giving high latency. (There is not much traffic there to handle ) 
• I checked the CPU usage of core, It is also normal.

What is the reliable and accurate method to test latency of the connectivity to the switches.

(Here I used ping to the VLAN interface IPs of the different VLANs. What is the recommended method).

[devils_advocate · Accepted solution]

The core is going to be a busy switch so I could believe the latency to one of its management addresses would be higher than an access switch. Out of interest, what is the response times in comparison to the access switch?

What are you trying to test in regards to latency to the switches management addresses?

If you want to run a ping to the management address of your switches then first get a baseline and go from there. If (for example), 5ms is the baseline average to the core then anything drastically above that suggests there 'could' be an issue.

Personally, I do not use a ping to a switches management address as a reliable method of proving anything. 

[nizarkotakkal]

@  devils_advocate

Thank you for your response,

When considering 5ms as baseline average,the result am, getting  is not much high.

Can you suggest me a reliable method to test or monitor and to get an output of the network quality.

What are you trying to test in regards to latency to the switches management addresses? - 

-- Actually trying to get a network status report by saving the ping status to text file for submission.

And I am doing it not only for management addresses, doing it for other servers and segments.

[davidpressler26]

Try going over your etherchannel configurations. Make sure everything is configured correctly.

show etherchannel 

channel-group	(Optional) Number of the channel group; valid values are from 1 to 64.
port-channel	Displays port-channel information.
brief	Displays a summary of EtherChannel information.
detail	Displays detailed EtherChannel information.

[nizarkotakkal]

Hi davidpressler26

     I will check the status and update.

Thank you

[Jon Marshall]

Totally agree with this.

There are a lot of other things those switches will be doing so ICMP will not be a high priority.

For general network performance you should test end to end devices and not to switch management IPs.

If you want to monitor your switches then you would be better off keeping CPU and memory statistics so you can compare if you see a performance issue in your network.

Jon

[nizarkotakkal]

Hi Jon Marshall

     Thank you for the information

[nizarkotakkal]

 Hi  devils_advocate

  Thanks for your response.

If keeping 5ms as baseline, the result is not much high.

What are you trying to test in regards to latency to the switches management addresses? - 

Actually I am saving the ping result to a text document for a submission about the network quality.

And I am trying the ping not only to the management IP, but also to the other segments like servers .

• May you suggest me the accurate and reliable method to monitor and test the network quality.

thank you