Local LAN Latency

[ssweehinlew]

There is latency when performing ping test  to the vlan interface IP (gateway IP) from the stackable access switches, Cisco 2960X to core switches C3650S. The ping response time is from 5 ms to 33 ms. The ping from host to host is <1ms. It has uplink throughput is 4Gbps. I have checked the cpu usage/memory and uplink. It looks fine to me. 

Anything else I can check. Please advise. 

[InayathUlla Sharieff]

1- check Physical layer then ( Interface errors/cabling/patch-panel if there is 0.

2- Then check connecting laptop and ping observe the result.

3- Is this new setup or existing? If existing has this ever worked fine? if yes then what changes(h/w or S/w ) been performed?

[ssweehinlew]

It is the new setup. All the switch ports are giving the same result. No issue on the physical layer.

[Joseph W. Doherty · Accepted solution]

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Posting

Ping wasn't really designed for performance testing, it was designed more for confirmation that a device is "alive".  This being the case, network devices often give little priority to responding promptly to a ping requests, and hardware switches do this on their control plane, which is relatively slow compared to their data plane.

I.e. 5 to 33 ms, from the switch, might be perfectly normal compared to the host ping being less than 1 ms.

[Alexey Stytsenko · Accepted solution]

Agree with Joseph.

Such ping can be normal, in case of the some control plane protection implemented on one of the end network devices between which you sent pings. You can check this by issuing more pings and monitor how RTT will increase with the increasing number of ICMP packets sent.

Example from my network:

SW01#ping x.x.x.x        

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to x.x.x.x , timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/17 ms

SW01#ping x.x.x.x  repeat 100

Type escape sequence to abort.

Sending 100, 100-byte ICMP Echos to x.x.x.x , timeout is 2 seconds:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Success rate is 100 percent (100/100), round-trip min/avg/max = 8/26/671 ms