Fast Ethernet errors, input overruns and ignored packets

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Feb 2nd, 2007

What is the most common problem for receiving input overrunns and ignored packets on a fast ethernet router card. I set the input hold queue to the max and they slowed down but are still incrementing. I am not getting any CRCs or Frame errors.

I have this problem too.
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glen.grant Fri, 02/02/2007 - 08:49

Means whatever interface the other end is attached is sending traffic faster than the interface can process it . Is the interface itself very busy ? Can be caused by having a lot of interfaces on the other end that are say gigabit and they are all trying to send traffic down this same pipe or the link is just overloaded.

jfresolone Fri, 02/02/2007 - 08:58

This is basicly a point to point. The other end is a Verizon 100 meg ethenet connection to the Internet. They have it shaped to burst only to 50 meg. The 5 minute input average on the interface is no more than 10 meg. They do have a transciever inline taking the ethernet for fiber to copper.

glen.grant Fri, 02/02/2007 - 09:12

I would verify with verizon on how the tranciever is setup whether it is set as auto or is it hardcode to 100/full , you may have a speed/duplex mismatch if traffic is that low . Must match on both sides .

jfresolone Fri, 02/02/2007 - 10:11

There was a mismatch when they first installed the unit. I was getting tons of CRC errors until I changed the setting from Auto Negotiate to 100 full on the unit. I thought I had the problem fixed but then I started getting just the ignored and overrun errors. Both sides are set static to 100/full

cmccormick Fri, 02/02/2007 - 21:33

Sounds like the router and/or port is just too busy to handle the traffic. With a 50M burst then probably not the raw load if this is the only busy port in the router. What router mode, what else is it doing? Are you running CEF? What is the CPU load on the router? Even an older 2621 can handle simple L3 forwarding at 50Mbps if the packets are not all 64 and the routes/route cache are not getting flushed all the time. Really need more info here I would think. Where is the traffic going? Are the output destinations allowing this traffic the exit quickly?

jfresolone Mon, 02/05/2007 - 05:06

The router is a 7204 / NPE400 ....CPU runs at about 8-10%. CEF and Fast switching is turned on. The outputs are 2 100 meg ethernets that are load balacing the traffic into a 3750 L3 switch that sits behind the router. So basicly traffic comes in from the internet on the 50 meg ethernet and traffic is then routed on to the two 100 meg ethernets that go to my network. The two output ethernets are running clean with no errors.


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