If you have a problem with the IPv6 multicast discovery during the VxRail initial cluster deployment, here´s another option!!
You can add hosts via IP address by klicking the + button in the top right corner and add all hosts by IP Adress and root password.
But first you need to configure the IP settings on each hosts directly on the command line:
Set gateway, IP adress and subnet mask for vmk2
esxcli network ip interface ipv4 set -i vmk2 -t static -g [x.x.x.x] -I [x.x.x.x] -N [x.x.x.x]
Set VLAN for vmk2 communication
esxcli network vswitch standard portgroup set -p "Management Network" -v[xxx]
Now you can go back to the VxRail Manager and add all hosts with the above configured IP addresses.