Active DAC with Mellanox ConnectX-2 EN?

[logan893]

I've got two Mellanox ConnectX-2 working well with a Cisco branded 5 meter passive DAC. I read the firmware changelog which says up to 7 meter DAC support had been added. I assumed this was a constraint for passive DAC only.

I have a 10 meter, also Cisco branded, active DAC. This cable does not work.

Has anyone used active DACs, and over 7 meters long, with this card?

 

[charlie]

Hi,

Passive DAC cable can be only max 5 meter length, above 5 meter only active DAC existing.

 

[BackupProphet]

If you need long cables, you're most likely cheaper off with fiber anyway. Tranceivers can be had for $1o each on Ebay and a 10meter cable should cost around $10 too. So that is total $30.

 

[logan893]

Thanks.

I have SFPs and fiber available, although the cable path is not optimal. I'll go with the fiber, and just try to be careful around the cable when vacuuming etc.

 

[HorizonXP]

Well, I'm running into this now. I definitely need to use an active DAC, and it's the Cisco-branded SFP-H10GB-ACU7M that I'm using. Going into a datacenter, and I don't have control of the switch it's going into, so I can't just go optical and get my own transceivers.

Has anyone gotten this to work?

 

[i386]

With active dacs you might have the same trouble as with optical trasnceivers. (If the switch doesn't like the vendor of the active dac it could block the link.)

 

[HorizonXP]

Turns out, it's the other way around. With the Mellanox card, it won't come up. But on an Intel X520, it comes up fine with this cable.

The switch side recognizes that it's a Cisco SFP/cable. The Mellanox card doesn't recognize it, and I can't seem to figure out which utility to use to help diagnose it.

With active dacs you might have the same trouble as with optical trasnceivers. (If the switch doesn't like the vendor of the active dac it could block the link.)

 

[i386]

There are a few cli tool in the Mellanox oefd package that can help to troubleshoot problems, but I'm not sure if they all work with the ethernet cards.

 

[Jerry Renwick]

I've got two Mellanox ConnectX-2 working well with a Cisco branded 5 meter passive DAC. I read the firmware changelog which says up to 7 meter DAC support had been added. I assumed this was a constraint for passive DAC only.

I have a 10 meter, also Cisco branded, active DAC. This cable does not work.

Has anyone used active DACs, and over 7 meters long, with this card?

I agree with Charlie, DAC SFP+ Twinax cables integrates SFP+ modules and Twinax cables on the same conduit. It usually comes in active DAC twinax and passive DAC cables.

For distances >5m and <10m, pickup the active version. Otherwise passive direct attach copper cables should be fine. So it is advisable for you to choose the active DAC or just go for SFP+ SR and OM3 cables.