I have installed 30 2921 ISR G2 routers on 24 sites. I am now seeing high output drops but can't figure out why. Help

Unanswered Question
Jul 12th, 2010

I have tried to recreate the setup in a lab but no joy.

The speed and duplex are the same on all connected devices (10mb full duplex) and the throughput is only about 5mb/sec.  They are running IOS v15.0

Has anyone seem this problem before.  If the fix is an upgrade to the IOS can you tell me where in the bug fix it is listed so I can put through a change control with evidence.  This is very important as I can't replicate the problem in the lab.


I have this problem too.
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Reza Sharifi Mon, 07/12/2010 - 14:22

All on board ports are 10/100/1000.  Are you also testing with 10mb speed in the lab?

niomanager Mon, 07/12/2010 - 14:29

The router is primarily in place to carry out MTU management and to allow me to collect netflow stats.  Upstream is a VPN concentrator which does the outbound routing.  Sometimes the router is directly connected to the concentrator and sometimes it goes via a 4500 switch.  All the WAN links are 10mb so it made sense to run the router at 10mb in/out.  The downstream switches are all 4500s so they can do the buffering.

Nagaraja Thanthry Mon, 07/12/2010 - 14:28


Can you let the devices auto negotiate the speed/duplex instead of hardcoding? Sometimes due to hardware incompatibility, they may not work well together. Negotiation makes sure that they exchange their capabilities. Also, since you are talking about output drops, I suspect your input rate to be higher than 10 Mbps (few bursts may be). Also, when you say that you have a link of 10 Mbps, it is not always true that you will get full 10 Mbps throughput. Typical throughputs range between 7 - 8 Mbps (Application).

Hope this helps.



niomanager Mon, 07/12/2010 - 14:31

I can drive 9.8mb through the whole setup in the lab with no increase in output drops.


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