Ping times from switch management IP's

[Michael Sales]

Hello all.

when I ping from device to device on a single switch, I get <1 ms times. But, if I ping the management IP bound to VLAN1 on that switch itself, I get 1ms to 15 - 20ms back.

I have idea's why, but I want to hear other opinions...

thanks

[johgill]

This is because the path is different. When pinging through the switch, it will be hardware switched. When pinging to the switch, it must interrupt the CPU from it's normal operation to process the packet and then generate a new packet. This is simply software vs. hardware.

[Michael Sales]

Thank You for your reply.

That is what I assumed it was.

[Bobby Thekkekandam]

Hi,

First of all, ping is a reachability tool, and not a very good tool for measuring performance or response time.

As far as the disparity between ping _through_ the switch versus pinging _to_ the switch, there are two reasons for this.

First, packets that are destined to the switch are processed by the CPU, whereas packets destined to devices connected to the switch are processed by hardware ASICs in the switch. Process switched packets are always handled at a reduced performance.

Secondly, the switch process responsible for responding to ICMP packets has a very low priority, as the switch's main job is to process network traffic, rather than respond to pings.

HTH,

Bobby

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[Michael Sales]

Thank You for your reply.

That is what I assumed it was.