hello, I'm trying to implement it using RB1100AHx4 and CRS317-1G-16S +
Exactly, the router RB1100AHx4 implements NAT and generates LACP to connect to CRS317-1G-16S +.

**What I tried.
Router RB1100AHX4 set ether1 = WAN1, ether2-3 = LAN1, LAN2 The WAN1 interface uses DHCP-CLIENT, and LAN1 and LAN2 are processed as bonding 802.3ads. After creating a group called BRIDGE "bridgeA0", we added bond1 to the "bridgeA0" group and ether10 for client testing. You have also added NAT rules.

ip allocation bond1= 192.168.10.2 , ether10 = 192.168.10 [ router to client test]

Problem situation: I connected router and client through ether10 and confirmed that it was not Internet.

[command]
/ interface
set [find name=ether1] name=WAN1
set [find name=ether2] name=LAN1
set [find name=ether3] name=LAN2
/ ip dhcp-client
add interface=WAN1 add-default-route=yes use-peer-dns=yes
/ interface bonding.
add slaves=LAN1,LAN2 mode=802.3ad lacp-rate=30secs link-monitoring=mii transmit-hash-policy=layer-2-and-3
/ interface bridge
add name=bridgeA0
/ interface bridge port
add bridge=bridgeA0 interface=bond1
add bridge=bridgeA0 interface=ether10
/ ip address
add interface=bridgeA0 address=192.168.10.1
add interface=bond1 address=192.168.10.2
add interface=ether10 address=192.168.10.10
/ ip firewall nat
add chain=srcnat action=masquerade out-interface=WAN1
add chain=dstnat dst-address=WAN1 address action=dst-nat to-address=192.168.10.0/24
add chain=srcnat src-address=192.168.10.0/24 action=src-nat to-address=WAN1 address

I want you to help me.

What is the purpose of router LACD to switch?
The switch does not need it, device such as NAS typically need it and in that case it would be switch to devices ????

I am grateful for your reply first.
As I am Korean, English can be unnatural.
The reason why I realize LACP load balancing between routers and switches is to connect to the server and operate it smoothly by increasing bandwidth. I am operating OPENSTACK, which is not the purpose of NAS.

Your explanations are very good!
I am not aware of built-in lacp type functionality in the router, but perhaps someone else is familiar with this requirement and can add their expertise.

I would get lacp working between the switch and the server first before deciding if more is needed between the router and the switch.