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tedauction
tedauction
New Member
April 20, 2020
Question

Reverse routing possible ?

  • April 20, 2020
  • 1 reply
  • 5214 views

Hello, is there any way to set up routes based on the reverse of RFC1918 private addresses i.e. any route that does NOT match:

192.168.0.0 - 192.168.255.255 172.16.0.0 - 172.31.255.255 10.0.0.0 - 10.255.255.255[/ul]

    1 reply

    lobstercreed
    lobstercreed
    New Member
    April 20, 2020

    I imagine there are ways to achieve your goals.  Can you give more details?  Blackhole routes and policy routes come to mind depending on the problem you're trying to fix. 

     

    For example I use blackhole routes to ensure that I don't send any RFC1918 traffic to the internet.  If I have a more specific route on a LAN link then it will take that first, otherwise it is dropped.

    tedauction
    tedauctionAuthor
    New Member
    April 20, 2020

    Hello, I am wanting a way to route all non-private address destinations to a particular port without using a 0.0.0.0 default route.

    Are there any options ?

    lobstercreed
    lobstercreed
    New Member
    April 20, 2020

    I'll have to avoid getting into a philosophical debate on why you don't want to use a default route for its basic purpose...  

     

    Policy routing might be able to achieve what you want.  You'll still wind up using a default route of sorts but it will be at the bottom of your policy routes to send traffic to the particular port. 

     

    Above it you would include 3 rules that say if the destination is 10.0.0.0/8, stop policy routing, then the 2nd rule would do the same for 192.168.0.0/16 and the 3rd for 172.16.0.0/12

    Only if the traffic passed all 3 rules excluding RFC1918 traffic would it match on the destination 0.0.0.0/0 to go out the specified port.

     

    I've actually done something similar to handle failover to a tiny backup Internet circuit.  I want most of my users to stay stuck on my main circuit even if it's down so they don't squash the little guy.

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