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high latency and packet loss in lan

Posted on 2011-09-10
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Last Modified: 2012-05-12
hi,

im using 2 cisco 3560e Giga,  with 4 etherchannel uplinks with vpan trunks, configured with hsrp on of the switches is active for all vlan ( i have 4 vlans).

i have 3 esx servers connected on both equipments for the HA.

Since a few time i have some packets lost if i ping between 2 machines in the same vlan or different vlan, the latency is minimum 1 ms average 2 ms and maximum 34 ms for repeat count of 1000 packets

the ping with maximum size make too much losts !!!

so any one have a suggestion ?
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Question by:jamill
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9 Comments
 
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Expert Comment

by:eeRoot
ID: 36517610
how are the ESX switch ports configured
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LVL 57

Expert Comment

by:giltjr
ID: 36517710
Define "maximum size".

How many are lost?

How busy is the server(s) while you are doing this?
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Author Comment

by:jamill
ID: 36521424
Hello eeRoot

the esxi switchport is configured like ine the scheme 1 cisco
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Author Comment

by:jamill
ID: 36521476

hello giltjr

here is a sample of a ping

ping 10.10.10.52 repeat 1000 size 1800

Type escape sequence to abort.
Sending 1000, 1800-byte ICMP Echos to 10.10.10.52, timeout is 2 seconds:
!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!
Success rate is 99 percent (994/1000), round-trip min/avg/max = 1/8/151 ms
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LVL 57

Expert Comment

by:giltjr
ID: 36524427
Well, although I would expect 100%, 6 dropped packets out of 1000 is not that bad.

What is your MTU?   Have you enabled jumbo frames?

You are using 1800 bytes.  The default LAN MTU is 1500 bytes.  If you have the default then you are fragmenting every packet.

If you want to test without fragmenting you need to specify 1472 instead of 1800, unless of course you have jumbo frame enabled.  If you have jumbo frames you need to specific "MTU-28" (IP and ICMP headers are 28 bytes together).

What happens if you do not specify a size and let it default?
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LVL 22

Expert Comment

by:eeRoot
ID: 36526376
Can you show the port configs from the ports on the 3560's that are connected to VMNIC's 1 and 2?
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Author Comment

by:jamill
ID: 36527671
hello giltjr

My MTU is the standard one 1500.
No im not using jumbo frames so should i ?
when i do not specify the size, i have 0% of loss and the maximum latency time is reducing



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Expert Comment

by:rfc1180
ID: 36530616
Well, although I would expect 100%, 6 dropped packets out of 1000 is not that bad.
I would disagree, any amount of packet loss is bad, especially utilizing TCP. Any packet loss is considered to be the result of network congestion and the congestion window size is reduced dramatically as a precaution. Your packet loss could be a result of many different factors and without some detailed troubleshooting and information, we will not be able to assist, we would only be assuming. please provide the configuration of your 2 switches, ensure that your port descriptions on configured on the ports so that we can identify what NICs are connected to what ports. Also, provide some screen shots on the vswitch configuration.

just as a test to rule on multihoming issues, remove NIC 2, and retest with 1800 bytes and report back.

Billy
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Accepted Solution

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giltjr earned 500 total points
ID: 36531706
Try specifying a size of 1472 and see what happens.

As I stated before, going larger than what a single Ethernet frame (MTU) causes fragmentation.  Once you have fragmentation there are other issues that can cause lost packets.

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