7206VXR NPE-G1 Gigabit Interface Overruns

[d.poppleton]

I just upgraded my 7206 from an NPE-400 to an NPE-G1. It is a WAN router connected to a core switch (6500). The connection between them (as a point to point routed link) was 100/full, and is now 1000/full over copper. The Gigabit interface on the router is now reporting overruns, and I am seeing packet loss in an IP Video application that runs over the WAN. I didn't see that with the NPE-400.

In the TAC case colletion I found this:

http://www.ciscotaccc.com/core/showcase?case=K18225106

It states: "On some interface types, this chipset and packet buffer cannot handle a long burst of frames. Such interfaces are meant to provide connectivity to a certain network type, and not to switch packets at line rate. The line rate of these interfaces is often higher than the switching capacity of the router."

A solution would be to slow down the traffic coming from the 6500, but I would like some suggestions on how to do it. QoS on the 6500 isn't an option at this point. Enabling flowcontrol on the switch?

I just can't believe I have problems on a gigabit interface that is only passing about ~35Mbps.

[d.poppleton]

Would you happen to have a bug ID for the flow control issue?

[Gregman380]

Sorry I do not have that information. This is what Cisco TAC sent me: "There are several bugs with flow control in 12.3T, so please upgrade to

12.4(19) to get all of them."

[d.poppleton]

Did you have an input service-policy on the interface? I just found this interesting bug (I have QoS coloring inbound on my interface, and I am thinking of trying to move that to the 6500). Bug is terminated, with no fixed in version.

CSCsh62765 Bug Details

Overruns seen on interfaces of NPE-G1 after applying QOS

Symptom:

Customer is seeing inout overruns on NPE-G1 native gigabit ethernet. Traffic flow is less than 1 mb in both directions.

Conditions:

Only seen on native interface when input service-policy is applied.

Workaround:

n/a

[d.poppleton]

I just wanted to update that moving the QoS coloring down to the 6500 did appear to resolve the issue. I am down to

I appreciate all the replies and suggestions from everybody!

[bcoverstone]

I can confirm that this is fixed by enabling flow control.  If you run "show controller gi0/1", you can see the rx_overflow and rx_int_drop values will precisely follow the input errors.  Unfortunately you can't increase the rx_ring, as it is hard coded at 128.

What you can do is turn on flow control.  This can be done by making sure that either the speed or duplex are set to AUTO.  When you do a "show int gi0/1", you will see this line:

 output flow-control is XON, input flow-control is XON

If you see "output flow-control is unsupported" then it is not on.  Check the speed/duplex settings again, and make sure they are AUTO.

Now, before this will be fixed, you will need to turn on flow control on your switch port.  It's enabled using the following command on a 2960/3560.

int gi0/1

flowcontrol receive desired

That's it.  No more errors.  You can also verify that you are getting pause frames from the router by running the following:

show flowcontrol int gi0/1

Port       Send FlowControl  Receive FlowControl  RxPause TxPause
           admin    oper     admin    oper
---------  -------- -------- -------- --------    ------- -------
Gi0/1      Unsupp.  Unsupp.  desired  on          8       0