On my freebsd, when ip and network conf is given by the dhcp, these routes are added for unknown reason :      54:a0:xx:xx:xx:xx  UHS    re0_vlan100      54:a0:xx:xx:xx:xx  UHS    re0_vlan100

The mac address is the one of my computer interface, and the IPs are for the local DNS servers :

root@ox2:~ # cat /etc/resolv.conf 
domain localhost.localdomain
nameserver (opendns manually added)
nameserver (google dns manually added)

Which are given by dhcp :

lease {
   interface "re0_vlan100";
   option subnet-mask;
   option routers;
   option domain-name-servers,;
   option broadcast-address;
   option dhcp-lease-time 172800;
   option dhcp-message-type 5;
   option dhcp-server-identifier;
   renew 3 2017/9/27 10:27:40;
   rebind 4 2017/9/28 04:27:40;
   expire 4 2017/9/28 10:27:40;

Because of these routes, querying the defaults dns fails. Deleting the routes fix the problem, until the lease is renewed...

Where do these routes come from ? And how do I stop them ?

I've tried on several networks with completely different isp/router, this happens every time.


The S designation (as part of the UHS in your example) means that it is manually added to the routing table. Could be that these entries are in your /etc/iproute2/ files?
If that doesn't show anything, run a grep to find the files they exist in by:

grep -R "" /etc

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