[j-nsp] MX routers and DAC cables?

[Eric Krichbaum]

That's what I was going to chime in on.  Behaviour differences between
software versions have done different defaults.  

ekrichbaum at atl-bdr1> show interfaces et-0/0/1 | grep FEC        
  Active defects : None
  Ethernet FEC Mode  :                   NONE

eric at cht-bdr2> show interfaces et-0/0/1 | grep FEC 
  Active defects : None
  Ethernet FEC Mode  :                  FEC91

These are 204s with a difference in default from 17.4 to 18.2 somewhere.
Manually setting FEC on both ends seems to correct and bring up the links.


-----Original Message-----
From: juniper-nsp <juniper-nsp-bounces at puck.nether.net> On Behalf Of Tobias
Heister
Sent: Friday, June 12, 2020 2:03 PM
To: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] MX routers and DAC cables?

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
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