I created a 802.03ad bonding on 3 interfaces, then tag it to a VLAN, and I need to apply a CoS priority on some packets :
set [ find default-name=sfp-sfpplus1 ] auto-negotiation=no loop-protect=off
name=ONT speed=2.5G-baseX
/interface bonding
add lacp-rate=1sec mode=802.3ad name=Router slaves=ether3,ether5,ether7
transmit-hash-policy=layer-2-and-3
The issue is that the bond is not usable like a port in the switch rules; so for having the priority and today I use a bridge filter which is not the best case as all packets have the priority applied.
/interface bridge vlan
add bridge=bridgeWAN tagged=Router,ONT vlan-ids=832
add bridge=bridgeWAN tagged=Router,ONT vlan-ids=840
Unfortunately, bridge filter rules cannot match on the IP and TCP/UDP headers inside VLAN-tagged frames, so you would have to create a separate bridge for each VLAN to be able to set the priority field value for DHCP in particular. But what Mikrotik model are we talking about? Maybe it supports switch chip rules that could be used for this, as these often allow to match port numbers in VLAN-tagged frames?
Try /interface ethernet switch rule
add switch=switch1 ports=ether3,ether5,ether7 vlan-id=852 mac-protocol=arp new-vlan-priority=6
add switch=switch1 ports=ether3,ether5,ether7 vlan-id=852 protocol=udp dst-port=67 new-vlan-priority=6
At worst it will just not work.