[AusNOG] A question for carriers on autoneg

[Edwin Groothuis]

On 11/05/2014 6:50 pm, Chris Ricks wrote:
> First of all, this question is not one of criticism or anything of the sort - it's simply addressing an observation I've made over the last decade or so. As always, I'm happy to be pointed in the right direction for reading historical posts on this subject
> 
> Almost without exception, any time a service is handed off over CAT5e/CAT6, the port parameters are hard set and auto-negotiation disabled. Most recently this was the case on a service handed off from a newly deployed Juniper switch to an EX4200 switch on our end. In another recent experience, a carrier worked with us to get a link up and, in spite of serious attempts to deliver the link through hard-setting of link parameters, we could only get the stability required via auto-negotiation.
> 
> I'm curious as to the thinking around auto negotiation being on or off for service handoff from list participants and their reasoning around the choice. 

As somebody who provides technical support for fail-to-wire capable
equipment often directly connected to to the telco equipment, I can tell
you it's a pain in the bottom.

Because it is fail-to-wire, it means that if the device gets turned off
(reboots, failures) that the two devices connected to it suddenly need
to reestablish an Ethernet link.

So under ideal circumstances you have the telco equipment on
auto-negotation, your equipment on auto-negotiation and the LAN side
equipment on auto-negotiation: Let them all deal with what they can do
and if the situation changes, they will renegotiate to what they can.
Happiness.

Then you get situations where auto-negotiation doesn't work, for
whatever reason. And one side of our device is then a fixed speed and
the other side is auto-negotiation. Fail-to-wire is then a not-so-happy
experience.

Or, even better, both sides are set to a fixed speed to make sure that
the fail-to-wire works but then the speed on the LAN side is way below
the output speed of our devices.

So, from my point of view, do auto-negotation with advertisement of all
possible speeds and let the network find out what works and what
doesn't. Your monitoring system should alert you if there are
frame-errors (or your network equipment should if it has support for
it). And check your failure scenarios to make sure that everything works
when things go wrong.

Edwin