Primary route confusion

[Kenth Eriksson]

Hi!

The primary route in BIRD, marked by '*', confuses me. Consider the
following two default routes as displayed by BIRD (2.0.2) and the Linux
kernel (4.14.51+).  

bird> show route 
Table master4:
0.0.0.0/0            unicast [ospf1 19:54:43.687] * E1 (110/350)
[172.20.4.41]
	via 172.20.4.41 on p1-1-1-1-2
                     unicast [kernel1 19:47:39.563] (40)
	via 172.20.0.1 on eth1


# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
0.0.0.0         172.20.0.1      0.0.0.0         UG    0      0        0
eth1
0.0.0.0         172.20.4.41     0.0.0.0         UG    32     0        0
p1-1-1-1-2

BIRD shows that the OSPF route with administrative distance of 110 is
primary, and not the kernel route with administrative distance of 40.

When BIRD pushes the OSPF route to the kernel, it uses the metric 32 by
default, whereas the default kernel route has metric 0. Both routes are
installed to the FIB, but the kernel will elect the route via eth1. Why
is not the default route over eth1 shown as primary in BIRD?

Can we control if BIRD pushes the OSPF route into the kernel here? The
kernel already has a more preferred default route.

Thanks,
Kenth