Swap route priority in different routing tables

[Gianguido]

Can I assign the same interfaces to two independent OSPF instances?

On 26/11/2020 13:37, Ondrej Zajicek wrote:
> On Thu, Nov 26, 2020 at 12:59:13PM +0100, Gianguido wrote:
>> Hi all,
>>
>> I have two sites, two links in between, one is high bandwith/high latency
>> (HB), the other is low bandwidth/low latency (LB), bird 1.6.8.
>> I neet all traffic to flow on HB link except for real time, which in my case
>> is RTP that goes through LB. To achieve this, I'm using PBR with two kernel
>> routing tables: main should have HB route as preferred route, low_latency
>> should have LB as preferred. Should any of the two fail, all traffic needs
>> to be routed on the other link.
>>
>> Problem is to properly populate the tables. Local interface states are not
>> reliable in terms of actual link availability, and anyways I'm already using
>> OSPF in the whole network setup.
>> Currently in bird OSPF runs and populate the main table, then I have a
>> dedicated pipe+kernel populating the low_latency one. Of course OSPF elects
>> the preferred route based on link costs, so only that route gets into bird
>> routing table, and it's the only one that can be eventually piped into
>> low_latency table. This way, all traffic goes either HB or LB depending on
>> OSPF link costs because the two routing tables are identical.
>>
>> Is there a way to get both routes learnt through OSPF into bird table and
>> then apply a filter to the pipe in order to swap the preference when
>> propagating those routes into the low_latency table? Or any other suggestion
>> to rework this in order to achieve the goal above?
> Hi
>
> Not really, OSPF does not work this way. You can use different routing
> protocols (e.g. BGP with BFD for quick failover), or use two OSPF
> instances with different 'instance id' and metrics.
>