High latency in LAN

[Paul Yang]

Hello,

We have one 2960S Switches and created Multiple VLANs. 

While Pinging from Member PC to Member VLAN IP on Switch, we are getting Higher TTL response.

But pinging from Member PC to Member PC, we are getting Normal Ping Response.

Is there any Problem in  Switch?

Thanks

Bacchus1001

[Mark Malone]

Hi can you provide some outputs so we can see what your talking about?

[Joseph W. Doherty]

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Posting

Generally, switches have special hardware to accelerate traffic that transit them, but when you ping the switch itself, the switch's general CPU usually responds.  First, since switches, as just mentioned, generally have special hardware for transit traffic, a switch's general CPU is often "small".  Second, switches also give little priority to responding to pings.  So, from both of these, a switch might show high latency to a ping yet it's working just as intended.

[Steve Fuller]

Hi,

I agree with Joseph.

Switches and routers treat the IP Input process that would handle ICMP packets destined to the switch with “normal” priority. All critical and high priority processes running on the switch are executed before any normal process so variation is to be expected on all but the most idle of devices. I just ran a quick ping to a Catalyst 2960 in my lab that has almost zero traffic, and saw minimum latency of 1ms and maximum of 7ms.

I posted about a similar issue recently in Ping reply peaks on router interfaces and in that post have some explanation of how IOS schedules processes.

Regards