Knowledge Base

Link Aggregation issues with Small Tree multi-port Gb cards & Cisco/other switches on Mac OSX.

Small Tree writes the Mac OS drivers for Intel based 2-port, 4-port and 6-port gigabit cards.  We support auto-negotiation of speed, duplex, flow-control (symmetric) and support Jumbo (up to 9216 bytes) frames.

All of these cards can be utilized on Mac OS with Link Aggregation (LACP) but Mac OS only supports one type of Link Aggregation, namely 802.3ad.  It is also known as Dynamic Link Aggregation.  This is different then Static Link Aggregation since static really means a "trunk"..... and is normally used to connect multiple switches together and not a Server or Workstation.

It has been found that many switches, including some Cisco's, do not support one or both of the following features:

Jumbo frames symmetric flow control

It is important to know what your switch supports that is connecting to the Small Tree gigabit card/ports. As an example, if your switch does not support symmetric flow-control (XON/XOFF in both directions), then you have to disable flow-control on the Small Tree gigabit cards (every port).  This is done using System Preferences GUI, Network tab:

Click on each of the ports and:

use the Advanced button,
select Hardware tab,
select Configure: Manually,
select Speed: 1000baseT,
select Duplex: full-duplex (not flow-control),
MTU: 1500 (you only change the MTU to jumbo at the "bond" level, not the port level)

Apply here and then Apply again when back to main Network section.  Repeat this for every port that will be part of the LACP/Bond.

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