I have 2x Arista Fiber Switches and they are working in MLAG mode and i want to connect 1 fiber from each arista to one of my juniper ex4200, so i want to know can i create lacp on juniper with these 2 fiber from two different arista without any issue or problem?
At the Juniper EX4200 you would create an AE that contain the multiple links, and then run LACP on top of this. LACP enabled is not default action for a Junos AE. On the Arista side, both their MLAG ports on the different switches should be configured to run LACP as well.
i want to just make sure they are comptible if i configure them in this way and there is no incompatibility,
Yes the standard ae with lacp is standards based so will be compatible with the MLAG link.