[systemd-devel] networkd: IPv6: equivalent of 'default via fe80::1` with policy routing?

[Mantas Mikulėnas]

On Fri, Sep 1, 2023 at 2:55 PM TJ <systemd at iam.tj> wrote:

> I may just be over-thinking this but I have a scenario that I can
> configure manually but have not been able to figure out how to amend the
> networkd configuration to match!
>
> # echo "2 starlink" >> /etc/iproute2/rt-tables
> # ip -6 rule add from 2001:0DB8:1:1::/64 table starlink priority 100
> # ip -6 route add default via fe80::1 dev WAN table starlink
>
> Note: 'via' required to prevent failed neighbour solicitations for
> external addresses.
>
> The issue is I cannot see how to achieve both 'default' and 'via' in
> .network
>   ROUTE section (when specifying a routing table).
> I see recommendations to use `Gateway=::` as an alias for 'default' but
> that prevents
>   setting the next-hop router address explicitly, which results in failure
> due to neighbour
>   solicitation.
>

No; `default` has nothing to do with the gateway field. It's an alias for
the route *destination network* field, specifically ::/0 for IPv6 or
0.0.0.0/0 for IPv6.

What you have is a completely standard IPv6 default route, regardless of
which table it's in:

[Route]
Destination=::/0
Gateway=fe80::1

-- 
Mantas Mikulėnas
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