PKTS are dropping in network

Unanswered Question
Dec 21st, 2009

Dear All,

IN our network we are having access switches , core switch 6500, ips and Fwsm .

When i ping to other vlan ip other device , i am getting drops . For 4000 sent packets 75 pkts are lost.

I check the configurations on devices ,trunks, speed ,access list etc all are correct.

what troubleshooting step i have to follow to solve this issue.

thanks,

m.k

I have this problem too.
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Ganesh Hariharan Mon, 12/21/2009 - 23:07

Hi,

Check step by step for packet loss !!

ping the server from the access switch and check is any packet drop is coming and as well as check the port error in which server is connected.

then ping the server FWSM and so on see where exactly the drop yuu are getting.

Also check the duplex setting from server top access switch.

HTH

Regards

Ganesh.H

mkareemashraf Tue, 12/22/2009 - 02:19

Hai Ganesh,

Thanks for u r response.

I already tried pinging servers from same subnet and different subnet .

If we ping in same subnet their are no drops and in different subnet there are drops.

I thinks because of IPS , packets are droping .

Note: Packets dropping -- one request time out after 60 pings.

But how to troubleshoot and  known exactly what is creating problem.

regards,

m.k

Ganesh Hariharan Tue, 12/22/2009 - 02:27

Make a monitoring port in switch where IPS port is connecting and sniff the traffic and do the same testing of continous ping for server from different zone.

One more thing check the duplex setting between IPS port and switch , And any error in those ports also.

HTH

Regards

Ganesh.H

vvasisth Tue, 12/22/2009 - 00:46

i think the 1st logical thing you need to check is where exactly are the packet drop taking place on the packet path

.

Try sniffing and check for interface counter errors on interface in b/w

Regards,

Varun

David Williams Tue, 12/22/2009 - 09:01

Without knowing the details regarding the packet path it is difficult to provide any specific troubleshooting advice.

  • I would start by inspecting the physical packet path, which has been suggested.  Duplex mismatches are a common culprit for packet loss.  If one side of an ethernet segment is hard coded and the other is set to auto negotiate, the auto negotiate fails and cisco defaults to 100 half on Fast Ethernet and 1000 Full on gig.  I'm sure you could see how the Fast Ethernet default could cause problems.
  • The other thing to consider is icmp is not a priority protocol.  Meaning, if you are pinging a router or switch, and that switch has something more important to do, it may drop or delay the icmp response.  You could try increasing the timeout on the ping to see if maybe you are getting the ping back, but outside the default timeout value.  You could try to do a capture as well, which has been suggested, but ideally I would try to ping THROUGH the network devices instead of TO the network devices.
  • You may also consider any shaping that may be done on physical or logical interface to see if you could be getting queue drops due to shaping.

Hope that helps!

DW

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