Duplex negotiation over 100Base fibre

Mon Feb 29 16:48:15 UTC 2016

>From all my observations, if both ends are 100Base-LX (or BX or T) and are set to auto-negotiate then they will negotiate to full-duplex. If one end is manually configured for full duplex and the other end is configured as auto then that end _may_ end up as half-duplex.

This is particularly true when connecting a 1G port to a port configured as 100M full-duplex port. If the 1G is configured for auto-speed then it _will_ negotiate to 100M half-duplex resulting in traffic impact.

HTH,

Nitin

________________________________________
From: NANOG <nanog-bounces at nanog.org> on behalf of Jason Lixfeld <jason+nanog at lixfeld.ca>
Sent: Monday, February 29, 2016 11:07 AM
To: NANOG
Subject: Duplex negotiation over 100Base fibre

Hello,

My understanding is that for 1G and 10G optical networks, there is no concept of half-duplex mode, but I’m unclear about half duplex in the 100M optical world.  Specifically, if I connect two 100Base-LX (or BX) transceivers together, is there a requirement for the controller(s on either side) to select between full or half duplex, either by static configuration, or auto-negotiation?

Thanks!