Best practices for connecting two CRS354-48G-4S+2Q+RM using XQ+DA0003 QSFP+ DAC cable?

Hi everyone,

I am connecting two CRS354-48G-4S+2Q+RM switches using an XQ+DA0003 40G QSFP+ direct attach copper (DAC) cable.

Since the CRS354 presents the QSFP+ cage as 4x 10G sub-interfaces (qsfpplus1-1 to qsfpplus1-4) and ROS v7 does not have a native "unsplit" / single 40G mode for this switch chip architecture (Marvell Aldrin/Aley), I configured a Bonding interface (LACP / 802.3ad) containing all 4 sub-interfaces.

Here is my current setup:

[admin@sw-ajt-00] /interface/bonding> print
Flags: X - DISABLED; R - RUNNING
0 R name="bonding-40G-ajt-qspfplus2" mtu=1500 mac-address=D0:EA:11:29:20:64 arp=enabled arp-timeout=auto slaves=qsfpplus2-1,qsfpplus2-2,qsfpplus2-3,qsfpplus2-4 mode=802.3ad primary=none link-monitoring=mii arp-interval=100ms arp-ip-targets="" mii-interval=100ms down-delay=0ms up-delay=0ms lacp-rate=30secs
transmit-hash-policy=layer-2 min-links=0 lacp-mode=active lacp-system-priority=65535
[admin@sw-ajt-00] /interface/bridge/vlan> print
Flags: D - DYNAMIC
Columns: BRIDGE, VLAN-IDS, CURRENT-TAGGED, CURRENT-UNTAGGED

BRIDGE VLAN-IDS CURRENT-TAGGED CURRENT-UNTAGGED

0 bridge 17 bonding-40G-ajt-qspfplus2 ether46
;;; vlan-gestio
1 bridge 5 bonding-40G-ajt-qspfplus2
;;; added by pvid
2 D bridge 1 bridge
bonding-40G-ajt-qspfplus2
;;; added by vlan on bridge
3 D bridge 5 bridge

[admin@sw-ajt-00] /interface/ethernet> print
Flags: R - RUNNING; S - SLAVE
Columns: NAME, MTU, MAC-ADDRESS, ARP, SWITCH

NAME MTU MAC-ADDRESS ARP SWITCH
53 RS qsfpplus2-1 1500 D0:EA:11:29:20:64 enabled switch1
54 S qsfpplus2-2 1500 D0:EA:11:29:20:65 enabled switch1
55 S qsfpplus2-3 1500 D0:EA:11:29:20:66 enabled switch1
56 S qsfpplus2-4 1500 D0:EA:11:29:20:67 enabled switch1

Can't tell if your post (excluding the title) is a question or a statement.

All four qsfpplus ports will always show up. If you connect the two switches together and configure just qsfpplus2-1 on both ends for 40G CR and the correct FEC mode, they will come up at 40G. That's how I had my 354 connected to a 326 for a while. (Now I have it connected to an MLAG stack, with two ports in one of the 326's and two in the other.)

Thank you for the detailed explanation. I'll adjust the port configuration and FEC settings as suggested.