Switching Latency Problem

Unanswered Question
Jan 26th, 2010

Hi friends,

I have a LAN which has one L3 Switch and 10 L2 switches. Those switches are connected through a gigabit Uplink.

Suddenly just one week back, i am pinging from End user to Server. The Reply time is increased from >1ms to 10ms.

Why this latency delay occur, how we can able to solve the problem.

L3 switch is 3560 and L2 Switches are C2960/C2950 switches.

I have this problem too.
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sachinraja Tue, 01/26/2010 - 11:06

Hi saravanan

where are the servers connected ? check for errors on the switchports ? see if you have any drops or CRC's on interfaces... is it 10 ms from all PCs on the network, or only from a certain Layer 2 switch connectivity ? Check for trunks and see if you have any issues there... try pinging the servers from the local switch, to check if there are any NIC issues with some servers....

Let us know

Raj

psaravanan Wed, 01/27/2010 - 06:47

Thanks, Mr.Sachinraja,

I checked all Ethernet port statistics. There is no error in the interfaces and trunk links.

Then i checked PC NIC card which takes more latency, this is also shows no error.

Then i checked the configuration of Switch port speed and PC also, both are in auto mode.

krishnakumarr Wed, 01/27/2010 - 08:23

Hi

First of all the PING is not correct tool to check the network perfomance .....

Check the applications side any slow responce for the users while accessing the servers

check the spanning tree flapping or interface flapping happning in the network

check the cpu utilization / load on L3 device

regards

krishna kumar

sachinraja Wed, 01/27/2010 - 10:59

I apologize if i had misunderstood your point, but Ping is definitely a very good tool to test network performance.. especially on layer 3... on layer 2, you can test Spanning tree misconfigs, application testing works on layer 5-7 etc... but on a LAN network ping response should be constant and not varying too much... if the network has some granular qos configurations,w ith multiple levels of priority or queues defined, sometimes PING can take lower precedence and can result in drops, but generally not on Gig LAN networks... sometimes it can also be due to layer 1 or NIC card issues, and not an issue on Layer 4-7 !

Saravanan - in any case, do you see performance issues due to this ? Can you let us know of your network more ? As krishna suggested, can you check the layer 2 - 7 performance too ?

Regards

Raj

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