To enable 32 bit AS numbers on your MLX-E you need to configure
capability as4 enable from BGP context:
capability as4 enable
[no] capability as4 enable | disable
[no] form of the capability command deletes the announcement and negotiation configuration of AS4s (if it has been enabled) at the global level.
Using the regular form of the command with the
disable keyword has the same effect on the global configuration. Disabling or using the
[no] form of the command does not affect the configuration at the level of a peer or neighbor.
The consequences of choosing between the
disable keyword are reflected in the output of the show running configuration command.
To enable AS4s for a peer group, use the
capability keyword with the neighbor command in the BGP4 configuration context.
The above clip is from page 1384 of 2728 in the NetIron MXLe Configuration Guide, document number 53-1001965-01 September 20, 2010.