Junos OS

Expand all | Collapse all

Route to Null (Discard)

Jump to Best Answer
  • 1.  Route to Null (Discard)

    Posted 11-14-2018 01:33
      |   view attached



    Another question:


    Given the attached diagram, I need to be able to configure a route to Null (Discard) in the following scenario (Note: I can configure discard for an unwanted route but this is different):

    Added for diagram: On the Core routers there is also an interface for Ethernet subscribers:


    Customer A on Ethernet enters the core (VoiP or Data) at THW-CORE-01 and sends to another site for Customer A out of the THW-LNS-01 to CPE Customer A. No problem. However, we have a situation (we believe) where if the connection to CPE Customer A goes down the route may loop between the Core routers (not sure) but what we need to happen, in that circumstance, if for the route to traffic to be dropped. But this should only happen if we LOSE that connectivity.


    Best way to resolve this please?


  • 2.  RE: Route to Null (Discard)

    Posted 11-14-2018 05:30

    Let me add a little bit more to this to try and explain it better:


    The routes to the dynamic LNS interfaces will be through the default route (advertised through IS-IS), so I guess I need to be able to route these destinations to "discard" if they are not in the routing table.


    Best way to achieve this please?

    Maybe create a policy or something with a higher preference than IS-IS so when IS-IS route is not there it takes that as the default?


    As always, I will investigate and test but thought I would ask.



  • 3.  RE: Route to Null (Discard)
    Best Answer

    Posted 11-14-2018 06:28

    Hi Clive,


    Do you want to add discard route for  subscribers IP's? Just create aggregate route with next-hop as discard.




  • 4.  RE: Route to Null (Discard)

    Posted 11-14-2018 07:24

    Hi Rahul,


    Thank you. I have resolved the issue in a slightly different way......


    Given that the address ranges being used are a little dispersed and cannot be aggregated easily, I am having to complete this in /24 blocks.....


    So, tested successfully:


    set routing-options static route <range> discard preference 167


    This works perfectly as 167 is above 160 IS-IS and below the BGP 170.