Hello, @Atkinson
Thanks for your reply.
With the settings for enabling IPv6, then the stack would support both ipv4 and ipv6, if you do want to only use the ipv6, then undefine of the ipv4 would be required.
Besides, you may need to set a ipv6 address for the test, for example,
netif_create_ip6_linklocal_address() API could be used, for details, I suggest checking the official site of lwip
BR
Chenyin