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ME 3800 output drops with Copper SFP

We have installed a copper SFP (GCL-T) in a access port on an ME-3800 running 12.2(52r)EY2.  The port connects to an ONS-CE-100 copper line card on an FE Port.  Both ports are set to auto-negotiate.  We see output drops on the interface.  We tried hard setting the speed on both sides, but the drops persisted.  We tried hard setting the duplex to full, but that made things worse.  On ports where we use the optical SFPs we do not see these issues.  

Has anybody else run into this issue? Does the ME 3800 support auto-negotiation with the copper SFPs?  Any thoughts on this would be appreciated. 

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Beginner

Hi Jim,

You would often see this kind of behaviour when traffic comes in on a gigabit port and then leaves on a 100M port, this is because the input rate is greater than the output rate. This does not imply you are doing 1gb/s input and only 100mb/s output but rather that traffic is entering your switch at a rate of 1gb/s for short micro bursts but the output port can only put the data onto the wire at a rate of 100mb/s. I’ve even see this kind of behaviour when doing traffic at rates as low as 1mb/s.

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Beginner

Hi Jim,

You would often see this kind of behaviour when traffic comes in on a gigabit port and then leaves on a 100M port, this is because the input rate is greater than the output rate. This does not imply you are doing 1gb/s input and only 100mb/s output but rather that traffic is entering your switch at a rate of 1gb/s for short micro bursts but the output port can only put the data onto the wire at a rate of 100mb/s. I’ve even see this kind of behaviour when doing traffic at rates as low as 1mb/s.

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I'm not familiar with the ME series, but if you can "tune" interface egress buffer/queue sizes, increasing resources for bursts can often mitigate and/or eliminate egress drops.  Of course, this also can increase latency.

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