setting network interface media/mediaopt

[tinus27]

hi all,

is there a way I can set my network interface to "100Mb full duplex"?
I have tried using ethtool but that doesn't seem to work. Complicating factor might be that the interface (eno1) is in a bridge.
I have access to the machine via IPMI/console.

gr.
tinus

 

[Ericloewe]

is there a way I can set my network interface to "100Mb full duplex"?

Why would you want to do such a thing? Why is 100BaseT even something you're concerned about?

 

[tinus27]

ah yes, good point.
The datacenter where this machine is located needs to cap the speed and they presumably set the switch port to 100Mb. Ever since they did that there is no connection. Restarting the server does not help.
looking at ifconfig output, the bridge (br4) and eno1 seem to be "UP"
"bridge link show" gives eno1 with "NO-CARRIER"

 

[jgreco]

If you are setting 100/full, you may also need to disable auto negotiation.

 

[tinus27]

actually, disabling autoneg doesn't work, whether I use ethtool or mii-tool, the eno1 interface keeps saying "Auto-negotiation: on"

 

[tinus27]

Issue is resolved after the datacenter set duplex to auto. not a truenas issue. Sorry to waste your time.

 

[Ericloewe]

Wow, that seems like a sleazy way of doing this, but I don't run a datacenter. @jgreco, what's your feeling on this practice?

 

[jgreco]

Wow, that seems like a sleazy way of doing this, but I don't run a datacenter. @jgreco, what's your feeling on this practice?

I'll give it three poop emojis. It's not really that unusual if we go back 20 years.

The '90's were filled with equipment with broken and poorly tested autonegotiation; it wasn't until 1000baseT that interoperable autonegotiation was mandated by the protocol, along with auto-MDI/MDIX. It was very common to fully specify media speed and duplex. This was just due to ethernet gear brokenness though.

Doing so in a colocation or data center environment as a method for rate limiting is pretty cheesy though. I've seen it done on gigabit fiber back in the aughties due to standards-noncompliant first gen gigabit hardware; I'm thinking the Foundry TurboIron 8 had some quirk with this. Rate limiting at speed in hardware is demanding on the hardware, and limiting link speed is much easier and less expensive than buying silicon designed to the task. Some peering exchanges such as AMS-IX have strong suggestions or policy about autonegotiation.