VLAN 30 was used as an example and could be any VLAN you want it to be. You could leave it at the default of VLAN1 if you wanted to. The peer to peer link will be be placed in Trunk mode and the keep alive packets are sent across layer 2. So the peer switches are not required to be in layer 3 mode.  In the example, Partner switch A and B are layer 2 switch. You would not assign an IP address to VLAN 30. You would only assign an IP address to VLAN 30 on the device performing routing on the network. you are treating the MLAG  
Hi, am i correct when i assume the newly introduced MLAG feature is only available on CLI and not via GUI? Best regards,Joerg  
FW 6.0.0.8 on 8164 (now N4064F) MLAG via GUI