Mikrotik OSPF Routing Distance Ignored

Discussion: Every routing protocol has a default distance to help the router to decide which route to use in case of multiple routes for the same destination. For Mikrotik routers these distances are listed here:
https://wiki.mikrotik.com/wiki/Manual:Route_Selection_Algorithm_in_RouterOS
If you want to configure a backup link that is only activated when the OSPF main route is missing, you can use a static route with distance 120 which is higher than the OSPF default 110.

If you enter this route in a mikrotik after the ospf route is learned it works as expected. The static 120 route is ignored until the ospf route vanishes.

But the other way arround does not work. If the 120 route is active, the OSPF route is ignored even it has the better distance of 110. And worse the Mikrotik keeps this route in its own OSPF announcement.

This is a known bug: https://forum.mikrotik.com/viewtopic.php?t=119493

Work around: You can make two smaller routes for the preferred path.
eg. two /26 should always overrule a /25 route.

Version: Mikrotik RouterOS 6.46.1

ARP and Broadcast Packets Missing

Problem: A Linux box with Debian 9 (kernel 4.9) on a HP server with Intel i40e (X710) network cards, is not reachable from neighbor machines, because ARP does not work.

Discussion: while testing with tcpdump ARP worked, but later ARP stopped working again. When tcpdump is used with “-p” (non promiscuous mode) you can see the problem. The server does not receive any broadcasts. Which means neighbors can not find the machine with ARP. Outgoing ARP does work though because ARP responses are not sent to broadcast the address (ff:ff:ff:ff:ff:ff).

Solution: A quick fix was to use “ifconfig eth0 promisc”. In this mode broadcasts are received and ARP is working. A better fix is to upgrade the Linux kernel to Debian 9 backports (4.19) or probably upgrade to Debian 10.

Versions: Debian 9 kernel 4.9 intel driver: 2.3.2-k intel firmware: 6.00 0x800034ea 18.3.6