Change LAN Port

I couldn't find my own post by searching, so I'm not even sure I asked this.

I currently have my LAN set to eth1.  WAN is eth0.  I would like to move everything to an SFP cable (eth7) on my ER-Pro.

Is there an easy way to do this -- basically change everything from eth1 to eth7?

 and  maybe some ideas?  

Thanks!