RFC8950 (IPv4 prefixes with IPv6 next-hop)

[wtremmel]

I started to model announcing IPv4 prefixes via an IPv6 BGP connection with an IPv6 next-hop and noticed that either I miss something or some additional filters would be useful for that.

I came up with the following template (only part shown):

...
 {%- if session | ip_version == 6 and session | has_tag("RFC8950") %}
     address-family ipv4 unicast
       maximum-prefix {{ session | max_prefix }} 95
      {#- more config details here #}
 {%- endif %}
...

Unfortunately this would choose the IPv6 max-prefix value and not the IPv4 one. I just chose max-prefix as an example, there are other issues.

Main question is: How to de-couple the IP version of the prefixes exchanged from the IP version setting up the session.

This might not be production relevant now, but with the decrease of available IPv4 prefixes even for IXPs might become relevant in the future (and RFC5549 where this was introduced is more than 12 years old, so it's time to finally use it).

best regards
Wolfgang