'RTNETLINK answers: File exists' error

Sometime in my firewall (based on debian), using my custom script and
with policy routing enabled, i hit this error:

 ifup vlan191
 Set name-type for VLAN subsystem. Should be visible in /proc/net/vlan/config
 Added VLAN with VID == 191 to IF -:eth2:-
 RTNETLINK answers: File exists
 Failed to bring up vlan191.

this typically happen when i 'play' with an interface (eg, i tear it up
and down many times for testing); after a bit of play (but something
suddenly) the interface go into a undefined state; interface is up (eg,
'ifconfig' return the correct data) but routing is a mess.


Sometime the only thing to do is reboot the firewall.


Probably i do something wrong in my script, but... how can i 'cleanup'
the mess without rebooting?


Thanks.

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