SR OS routers never send or receive IPv6 routes with 32-bit IPv4 next-hop addresses.
When an IPv6 BGP route is advertised to an EBGP peer, next-hop-self always applies (except if the third-party-nexthop command is applied, as described in the following note). Next-hop-self results in one of the following outcomes.
If the EBGP session uses IPv4 transport, the BGP next-hop encodes the local-address used for setup of the session as an IPv4-compatible IPv6 address (all zeros in the first 96 bits followed by the 32 bit IPv4 local-address).
If the EBGP session uses IPv6 transport, the BGP next-hop is the local-address used to setup the session and this cannot be overridden, even by BGP export policy.
When an IPv6 BGP route is re-advertised to an IBGP or confederation-EBGP peer, the advertising router does not modify the BGP next-hop by default; however, this can be changed as follows.
If the BGP next-hop-self command is applied to the IBGP peer or confederation-EBGP peer, then this changes the BGP next-hop to the local-address used to setup the session (if the transport to the peer is IPv6) or to an IPv4-compatible IPv6 address derived from the IPv4 local-address used to setup the session (if the transport to the peer is IPv4). This command applies to all routes advertised to the peer, regardless of the peer type from which they were received (IBGP, confed-EBGP, or EBGP).
If IPv6 routes are matched and accepted by an export policy applied to an IBGP or confederation-EBGP session, and the matching policy entry has a next-hop-self action, this changes the BGP next-hop of only the matched routes to the local-address used to setup the session (if the transport to the peer is IPv6) or to an IPv4-compatible IPv6 address derived from the IPv4 local-address used to setup the session (if the transport to the peer is IPv4).
If IPv6 routes are matched and accepted by an export policy applied to an IBGP or confederation-EBGP session, and the matching policy entry has a next-hop <ip-address> action, this changes the BGP next-hop of only the matched routes to <ip-address>, but only if <ip-address> is an IPv6 address. If <ip-address> is an IPv4 address the matched routes are treated as though they were rejected by the policy entry.
When an IPv6 BGP route is locally originated and advertised to an IBGP or confederation- EBGP peer, the BGP next-hop is, by default, copied from the next-hop of the route that was imported into BGP, with specified exceptions (for example, black-hole next-hop). When a static route with indirect next-hop is re-advertised as a BGP route, the BGP next-hop is a copy of the indirect address, however with route-table-import policies BGP can be instructed to take the resolved next-hop of the static route as the BGP next-hop address.