Hello,
the command "show ethernet-switching table" is mainly used on Juniper Switching platforms (EX , QFX series) , MX is routing platform, but still can support switching by using bridge domain feature, in this case, you can use the below command to check the mac table along with optional parameters listed below:
show bridge mac-table ?
Possible completions:
<[Enter]> Execute this command
<address> MAC address
bridge-domain Name of bridging domain, or 'all'
brief Display brief output
count Display count only
detail Display detailed output
extensive Display extensive output
instance Display information for a specified instance
interface Display MAC table for a specified interface
isid Display Information for specified ISID or all ISID(s) (256..16777215)
logical-system Name of logical system, or 'all'
vlan-id Display MAC address learned on a specified VLAN (0..4095)