Related: IPv6 multi-homing over CGNAT with BGP on RouterOS: https://blog.homestack.space/multi-homed-ipv6-cgnat-mikrotik/
This paste assumes a hardware MikroTik RouterBOARD with the standard MikroTik default config — hAP, hEX, RB5009-class, etc. — where ether1 is the WAN port and ether2 through etherN are LAN bridge ports. The paste removes ether2 from the LAN bridge and turns it into WAN2.
If your router is not in that default state — CHR, multi-WAN appliances, anything reconfigured, or anything where ether1 is not your WAN — read the full guide and substitute interface names. The lab report's §8.7 TL;DR validation shows the kind of remap CHR needs before this paste is safe.
Resulting layout after the paste: