OSPF for IPv4 over IPv6 only?

[Bernd Naumann]

On 30.01.24 10:32, Nico Schottelius via Bird-users wrote:
> 
> Good morning,
> 
> if we are talking about BGP, IPv4 routing over IPv6 works
> beautifully. We just add another IPv4 channel and get BGP MP.
> 
> OSPFv3 works fine on IPv6 and when creating two instances, one for IPv6
> one for IPv4, things look correct. But how does OSFPv3 conceptually work
> if the interface of the ospf area do not have IPv4 addresses themselves?
> 
> In the BGP case we can use "extended next hop on;" to use the IPv6
> nexthop for IPv4, but I did not find a similar setting for OSPF to
> accept IPv6 nexthops for IGP IPv4 addresses.
> 
> Is there a way to purely go IPv6 only and still relay stub network IPv4
> information via an IPv6 only internal area?
> 
> Best regards,
> 
> Nico

Hi Nico,

If every router has "at least" a /32 IPv4 address on loopback[1], you
could do "OSPF unnumbered". It's not IPv4 over IPv6 but you do not need
a bunch of IPv4 peer addresses on each and every interface.

[1] IIRC I had some issues with that setup a few years ago, _BUT_ you
can /just/ assign the /32 IPv4 loopback address on each OSPF interface,
too.

Otherwise: If you already have and can use BGP MP, why would you want
IPv4 in OSPF, too? (Curious questions...)

Best,
Bernd
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