[j-nsp] MX routers and DAC cables?

[Tobias Heister]

Hi,

On 12.06.2020 20:39, Chris Adams wrote:
> Is anybody using DAC cables on MX routers?  We have a customer with an
> MX10003 connected to EX4600 switches with 40G DAC cables (Juniper parts,
> not third-party).  Upon upgrading the router JUNOS to 18.2R3-S3, none of
> the interfaces with a DAC cable would come up on the router end.
> 
> JTAC's response was that no DAC cables are supported on any MX routers.
> 
> That seems a little odd to me... I thought DAC cables are a part of the
> various specs, so saying they're not supported is saying those aren't
> actually Ethernet ports to me.

DAC and AOC are transceivers, and officially only a specific set of 
transceivers are supported per platform.

For MX10003 you can check here: 
https://apps.juniper.net/hct/product/#prd=MX10003

There are 40GE AOC supported for that box, but not 40GE DAC. For 100GE 
DAC are actually supported in later Junos version.

That being said typically DAC worked in MX for 10G and even 40G on most 
noxes, but on MX10003 we had a lot of problems with 40G DACs and 
eventually replaced most/all of of them with optical transceivers.

Even on 100GE you might need to set the FEC config depending on what and 
where you connect the other DAC end.

While 10G mostly worked everywhere we had a fair share of trouble on 40 
and 100GE on various vendors and platforms.

-- 
regards
Tobias