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rpress
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i40e problem with DAC

Sat Aug 15, 2020 8:53 pm

1. Version 7.1beta1
2. CHR x86
3. Using the i40e driver, bring an interface up with a DAC already inserted and linked. The interface does not register "link ok". The DAC must be removed and plugged again to get the port to link.
4.
/interface ethernet
set [ find default-name=ether6 ] mtu=9100 name=ether6
5.

I have noticed a problem using the i40e driver. My adapter is an Intel X710-DA4. With a DAC in the SFP+ port, the interface does not register "link ok" when it is brought up. The DAC must be removed and plugged again to get the port to link. I also have a LR module (Edimax MG-10GAS1) and interestingly this does not have any problem. The problem occurs both on boot of the router and also if I manually disable and enable the interface.

The port shows it is receiving bytes, but there is no transmit. No surprise because it thinks the link is down.
   #      NAME                 RX-BYTE        TX-BYTE  RX-PACKET  TX-PACKET  R  T  TX-QU  R  T
   7  RS  ether6                 3 972              0         66          0  0  0      0  0  0

I didn't see this problem when using Linux.

Here is my DAC from ethtool:
	Identifier                                : 0x03 (SFP)
	Extended identifier                       : 0x04 (GBIC/SFP defined by 2-wire interface ID)
	Connector                                 : 0x21 (Copper pigtail)
	Transceiver codes                         : 0x00 0x00 0x00 0x00 0x00 0x04 0x00 0x00 0x00
	Transceiver type                          : Passive Cable
	Encoding                                  : 0x00 (unspecified)
	BR, Nominal                               : 10300MBd
	Rate identifier                           : 0x00 (unspecified)
	Length (SMF,km)                           : 0km
	Length (SMF)                              : 0m
	Length (50um)                             : 0m
	Length (62.5um)                           : 0m
	Length (Copper)                           : 1m
	Length (OM3)                              : 0m
	Passive Cu cmplnce.                       : 0x01 (SFF-8431 appendix E) [SFF-8472 rev10.4 only]
	Vendor name                               : CISCO-MOLEX
	Vendor OUI                                : 00:09:3a
	Vendor PN                                 : 74752-9519
	Vendor rev                                : 09
	Option values                             : 0x00 0x00
	BR margin, max                            : 0%
	BR margin, min                            : 0%
	Date code                                 : 120917
 
rpress
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Re: i40e problem with DAC

Mon Sep 21, 2020 3:02 pm

This problem is unchanged with 7.1beta2.

I have also tried a couple different SFP+ to copper transceivers. They also have this problem.

My theory is that there is a race condition with the link status. When using the LR fiber transceiver (the one which works fine) the link is a bit slower to come up. This additional time delay allows for the Mikrotik software to register the link up status. With the DAC and copper transceivers, the link comes up faster. This causes the Mikrotik software to miss the link transition.
 
rpress
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Posts: 111
Joined: Thu May 07, 2009 5:13 am

Re: i40e problem with DAC

Tue Dec 08, 2020 11:02 pm

This problem still exists with 7.1beta3.

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