Inject ethernet-based defaults to OSPF

[daniele]

Nice, will try that. One additional question: if leverage kernel 
protocol, it means local routing tables already contain the default 
learnt through DHCP. Wouldn't this generate some kind of warning (ie. 
bird4: Netlink: File exists) when bird, say on R2 to install R1 as 
default, tries to overwrite the local default with the one generated by 
OSPF?

cheers

On 19/09/2019 13:20, Ondrej Zajicek wrote:
> On Wed, Sep 18, 2019 at 11:53:30AM +0200, daniele wrote:
>> Hello list,
>> I???m looking for some advice from someone that has more experience. I'm
>> running bird 1.6.6.
>> I have two routers R1 and R2, each with a single internet uplink U1 and U2,
>> running OSPF and sharing a LAN ethernet segment. Both U1 and U2 are
>> dhcp-based ethernet segments themselves with a next-hop IP address that can
>> change. I want R1 to be the primary LAN internet gateway and R2 the
>> secondary. Should U1 fail, R1 has to route to R2 in order to reach internet
>> through U2.
>> How would you recommend to inject U1 and U2 default routes into OSPF? I
>> cannot use the next-hop ip address as it changes along time, and an
>> interface-based static route would not work.
> Hello
>
> I would suggest learn default route using kernel protocol (allow in
> import, option 'learn'). Then set ospf_metric2 in OSPF export filter
> (different on R1 and on R2).
>