ping time more than 1msec

[ikramullah123]

Hi,

we have more than 150 workstation in our network and many servers and more than 15 vlans, when i ping any vlan id , my ping time is not stable and changing with different numbers, anyone tell me the cause and the best solution for that?

thanks in advance

[Mark Malone]

Hi

Pinging a vlan id is not an accurate test and even looking that output it looks fine , when you ping a vlan in same subnet packet gets sent to cpu to be processed , when you ping to another vlan diff subnet it will be hardware switched not using cpu so the test itself is not accurate as both are bing processed by diff parts of the swutch , your relying on cpu not to be impacted or have any temporary spikes happening any fluctuation in cpu could alter the test.

the best way is to test between clients end - end do not rely on switches and routers for accurate pings or else use an ip sla responder which should give much more accurate results

[ikramullah123]

thank you Mark Malone for your answer

you know in LAN network normal ping time is 1msec, now i am talking about the causes and what will be the problems when my ping time more than 1msec, a day before we off all switches, router and server at that time just layer 3 switch was on when i ping the layer 3 switch there still the same problem, now can you tell me that where is the problem now ,? 

i attached some screenshot of my ping please look in to it.

[Mark Malone]

Yes but the pings still aren't an accurate test pinging a router or switch physical or logical interface on router/switch will not always give a accurate response

If you want to see if there is latency on the network test end - end client - client or use the ip sla feature which is designed for icmp testing like that , testing pinging interfaces on device is not accurate

[Joseph W. Doherty]

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Posting

As Mark has noted, ping is not highly accurate for latency measurements.  It's original purpose was more aligned to determine if a host is "alive".

As Mark has also noted, for accurate latency measurements you need to use an application designed for that.  SLA tests, against Cisco devices that support a SLA responder, will provide much improved latency accuracy.

[ahmedshoaib]

Hi;

We cannot judge our network on base of ping to the gateway (Switch/Router) IP address. Always judge on the bases of end to end communication (means client to server or server to server traffic flow). Mark is right whenever whenever pings a gateway/vlan ip in same subnet packet gets sent to cpu to be processed.

Take an example you network is running smoothly and ping time is 1ms or less then 10 msec, you start ping gateway and same time you start capture of show tech-support, you feel the ping time will start varies due to switch/router CPU utilization become high due to show tech-support command you run.

Yes, if there is a ping delay we need to identify what is an issue. For me there will 2 things you need to verify in your network:

1. Core Switch utilization & incoming/outgoing traffic.
2. The Spanning-tree is not properly configured on your network. A small switch becomes root instead of your main switch.

Please verify the switch CPU utilization, Core interface incoming & outgoing traffic if its high means you need to upgrade your switch. If your core switch is not spanning-tree root then reconfigure the spanning-tree value again in such a way that your core switch becomes root.

Thanks & Best regards;

[ikramullah123]

sorry i am talking about Gateway not vlan id, when i ping any gateway in the network it happen the same problem and come fluctuation and variation in ping time,