Solved

LAN connection with high delay on one hop

Posted on 2014-02-23
13
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Last Modified: 2014-03-04
Hi,

I was getting alert on ping fail from monitoring system on and off for several hours, after several hours, everything goes back to normal.

I looked into the problem and found that there was unusual high delay (between 35 to 60ms) on one hop (Cisco switch to a Cisco router), both ports are set with 1GB bandwidth. Never seen this problem before. No configuration was changed during time.

I have checked the input and output error on the ports, there's no error. Traffic was normal during the time. the ports were not flapping up and down.

What would be some possible causes of this issue?

Please share your knowledge all.

Thank you so much!
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Question by:tmatty102
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13 Comments
 
LVL 16
ID: 39881315
Can you give us some topology specifics? Is the switch and router in question on the same LAN segment? Do you have spanning-tree enabled on the switch to insure you don't have any routing loops?

MO
0
 

Author Comment

by:tmatty102
ID: 39881334
Hi MO,

Thanks for replying.

the topology is access switch to core switch to router and out to the MPLS Cloud. very straight forward.

Spanning tree is enabled to avoid routing loops. the port that connect the switch with the router is configured as layer3 port

Thanks
0
 
LVL 16
ID: 39881352
You're routing between core switch and router? Is that where the latency is occurring? Between core switch and router? Not between access and core switches.

MO
0
 

Author Comment

by:tmatty102
ID: 39881354
yes, correct.
0
 
LVL 16
ID: 39881357
Is there a particular reason you would be routing from your core switch to the local MPLS router? Do you have multiple different networks behind the core switch?

MO
0
 

Author Comment

by:tmatty102
ID: 39881362
No particular reason, the company has this setup when I join the company. Yes, I have multiple different networks behind the core switch.
0
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LVL 16
ID: 39881367
Have you contacted your MPLS provider to see if they can review interface statistics on there end? Perhaps they were showing errors on the interface that connects to your core switch.

MO
0
 

Author Comment

by:tmatty102
ID: 39881372
yes, They have verified that there's no problem on their end.

I have verified that the problem is between the router ( I managed the router not the MPLS provider) and the core switch. This is verified by using the monitoring system that we have; by comparing the RTT report from remote sites to the router and local probe to the router, the local probe to the core switch and the local probe to the router. The latency is confirmed to be between the core switch and the router.

I have checked the input and output error on the ports, there's no error. Traffic was normal during the time. the ports were not flapping up and down.
0
 
LVL 16
ID: 39881427
Any chance the monitoring tools themselves are reporting inaccurately? Is there any indication of a problem other than what the monitoring tools are reporting?

Does the latency occur regularly? If so, can you run some basic ping tests between the router and core switch to validate the results of the monitoring tools? Maybe setup ping plotter on a host sitting behind the core or access switch to monitor the LAN side IP of the router (e.g. the interface that connects to the core switch) and let it running in eval mode so you can compare results from it to your monitoring tools.

MO
0
 

Author Comment

by:tmatty102
ID: 39881450
this issue never happen before. We have an old and a new monitoring system, they both are reporting the same delay. This is the vrry first time it happens. It doesn't happen regularly.

That might be a good idea to set up a ping plotter. However, this issue seems to have resolved itself at this time. I couldn't find any clues after I checked the logs, port errors (there is any but there was no errors) as I mentioned.

Thanks for the help so far.

Please let me know if you can think of anything. I'm placing a call with Cisco to check on this as well in case I have missed anything.
0
 
LVL 16
ID: 39881604
Wouldn't hurt to get those guys on the line for a quick look over. They might coincide your explanation of the issue with a bug in the particular IOS you're running. It happens.

Sorry I couldn't get you any closer to a resolution on this one.

Good luck.

MO
0
 

Accepted Solution

by:
tmatty102 earned 0 total points
ID: 39892657
After the call with Cisco tech, they weren't able to find anything. The tech went through the steps that I have already done.
0
 

Author Closing Comment

by:tmatty102
ID: 39902800
The problem resolved by itself over time
0

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