On Fri, 2018-09-21 at 12:44 +0200, Ondrej Zajicek wrote: > CAUTION: This email originated from outside of the organization. Do > not click links or open attachments unless you recognize the sender > and know the content is safe. > > > On Fri, Sep 21, 2018 at 06:51:17AM +0000, Kenth Eriksson wrote: > > 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. > > Hi > > BIRD on Linux cannot overwrite alien/kernel routes in kernel routing > table. It uses kernel metric 32 to avoid collisions with them. > > > 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? > > That is because kernel protocol has low preference. Set it to higher > value. Set preference for kernel protocol to higher value than OSPF. > I see you have 40 and 110, which are not default values anyway.
So the preference value in BIRD is not the same as administrative distance? I believe both Juniper and Cisco treats lower preference value / administrative distance value as a more preferred route. https://www.juniper.net/documentation/en_US/junos/topics/reference/general/routing-protocols-default-route-preference-values.html Is preference value inverted in BIRD? > > > Can we control if BIRD pushes the OSPF route into the kernel here? > > The > > kernel already has a more preferred default route. > > If kernel route wins in BIRD table, then OSPF route will not be > pushed > to kernel. > > -- > Elen sila lumenn' omentielvo > > Ondrej 'Santiago' Zajicek (email: [email protected]) > OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, > wwwkeys.pgp.net) > "To err is human -- to blame it on a computer is even more so."
