nanog mailing list archives

Re: 10G switch drops traffic for a split second


From: TJ Trout <tj () pcguys us>
Date: Tue, 29 Nov 2016 13:28:22 -0800

Luke;

All l2, no l3. only 4 vlans. 2 peers trunked to a router which trunks back
to 2 devices (microwave backhauls).

Chuck;

All ports are 10g except the 2 peers are 1g and trunk back to a 10g port
for the router wan

No TCN's

Brian;

I have tried a IBM G8124 and a Ubiquiti ES-16-XG both show same exact drops
across all ports, makes me think it's a config issue. MTU, FC, something.

Andrew;

I have tried with FC disabled, but I will try that one more time.

Mikael;

Is it possible to over run the buffers of a 320gbps backplane switch with
only 1.5gbps traffic? I think the switch is rated for 140m PPS and I'm only
pushing 100k PPS


On Tue, Nov 29, 2016 at 9:47 AM, Mikael Abrahamsson <swmike () swm pp se>
wrote:

On Tue, 29 Nov 2016, TJ Trout wrote:

Could this be MTU? I've tried flow control, hard code duplex, stp on/off
etc


As others have pointed out, you probably have a switch with small buffers.

If you also have flow control and you have something that triggers flow
control to turn off packet forwarding, your small-buffer-switch might fill
up all (shared) buffers on that port and now you're dropping traffic to all
ports.

So trying to find if you have something where flow control is enabled and
is being triggered might be something worthwhile to do, and also perhaps
just turn off flow control on all ports to make sure.

--
Mikael Abrahamsson    email: swmike () swm pp se



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