Understanding network modules on MX7000 chassis

Hello,

I'm a network engineer and it's the first time i'm working on a dell chassis (MX7000).

I have a Windows server sled connected to A1 et B2, than these 2 switchs are connected to a JUNIPER switch.

My understanding is that only A1 is running and B2 is for backup in case of A1 is down. Is that right ? How and which protocol/mechanism is used to do that ?

What about the internal connection between my Windows server sled and the other switchs A2 et B1, are the internal ports to these switchs in shutdown mode?

And why do I have two internal connections from A1 to my Windows server sled as shown below ?

A1# show lldp neighbors
Loc PortID Rem Host Name Rem Port Id Rem Chassis Id
--------------------------------------------------------------------------------------
ethernet1/1/1 iDRAC-X1 X1 NIC.Mezzanine.1A-1-1 MAC1
ethernet1/1/6 iDRAC-X2 X2 NIC.Mezzanine.1A-1-1 MAC2

Thanks