BGP Cisco IOS IPv6
You will have to understand the MBGP address families. One of the basic rule of MBGP is that when I'm advertising a route from a specific address family, the next hop has to be from the same address family. So, you will have to make sure the next hop is from the same address family. Couple of examples for you: A basic rule of mBGP is that when advertising a route from a specific Address-family the next-hop address has to be from the same address-family, or you will have to use roue-maps.
IPv6 route through BGP IPv4 neighbor
To pass the NLRI - Next-Hop address -
1. IPv6 NLRI in IPv4
router bgp 300
bgp router-id 192.168.146.1
neighbor 192.168.151.1 remote-as 400
!
address-family ipv6
neighbor 192.168.151.1 activate
neighbor 192.168.151.1 route-map IPv6NEXTHOP out
network 2001:16d8:dd85::/48
!
route-map IPv6NEXTHOP permit 10
set ipv6 next-hop 2150:1:1::3IPv4 route through BGP IPv6 neighbor
2. IPv4 NLRI in IPv6 router bgp 300 bgp router-id 192.168.30.1 neighbor 2150:1:1::2 remote-as 400 ! address-family ipv4 neighbor 2150:1:1::2 activate neighbor 2150:1:1::2 route-map IPv4NEXTHOP out network 192.10.0.0 ! route-map IPv4NEXTHOP permit 10 set ip next-hop 150.1.1.3 </source>