why ping delay is more in L3 SWITCH

[Manjunath MR]

Hi,

   I have one L3 Switch & one router and i'm pinging to loopback IP address of both switch and router and result is as shown below

PC-------L3 switch-------router

PC to L3 SWITCH ping dalay min/avg/max= 8/12/74 ms.
PC to ROUTER ping delay min/avg/max= 1/1/1 ms 

Why switch is having more delay. is it due to ICMP packets handling in switch is by software (CPU) ?? 

How ICMP packet will be handle in L3Switch and ROUTER

[Mark Malone]

Hi

pinging to a an loopback interface on a switch will always give you varying results , only a ping end end is valid , the cpu could be doing something , resources in use etc when you ping a vlan interface or loopback so it will not be accurate as it is not giving priority to the icmp packet  , to get good solid results use ip sla feature  or ping device to device end -end like between pcs

sending packets icmp to an interface like that is process switching and will need to wait for the cpu to allocate it to schedule to return the icmp reply , if cpu is busy you get delayed response

[Manjunath MR]

Yes pinging to an loopback interface or VLAN interface on a switch always giving varying results. But CPU utilization is always <10% . 

We are using ZTE 8900E series switch and M6000-S series router. but the result is same...

In ZTE Switch there is no IP SLA feature. Is there any other way?

[Joseph W. Doherty]

Cisco devices are not optimized for providing fast turn around for a ping request, they are optimized for dealing with transit traffic.  If fact, to provide a better or more accurate ping response, Cisco SLA responders can indicate device processing delay so the sender can get a more accurate measure of network transit delay.

Why switch is having more delay. is it due to ICMP packets handling in switch is by software (CPU) ?? 

That's certainly a possible factor.  L3 switches do the bulk of their traffic forwarding using dedicated hardware.  They need their CPU for control plane functions.  "Small" routers, though, tend to do everything with their CPU.  So, in my experience, a "small" router may have a faster CPU than a "small" L3 switch which may indeed be able to process a ping reply quicker and/or with less timing variance.