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Weird "reject" on MX240 Core router

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  • 1.  Weird "reject" on MX240 Core router

     
    Posted 08-17-2018 02:15

    Hi,

     

    Quick look at topology:

     

    3a05:d840:0060:ff46::0/64 prefix --> xe-1/2/4.10 MX240 Core --> MX240 Core xe-1/2/5 --> Upstream Peer

     

    On the MX core I am advertsing the following to the eBGP upstream peer:

    3a05:d840::/29

     

    If I perform a route lookup for the "3a05:d840:60:ff46:701c:c6b7:44d5:d26b" IPv6 address, I am getting the following response:

    user@test# run show route 3a05:d840:60:ff46:701c:c6b7:44d5:d26b

    inet6.0: 50636 destinations, 50636 routes (50636 active, 0 holddown, 0 hidden)
    + = Active Route, - = Last Active, * = Both

    3a05:d840::/29 *[Aggregate/130] 2w1d 18:58:15
    Reject

     

    Not sure why it is showing the route as rejected. Here are the advertsied IPv6 Networks:

    Clive@THW-CORE-01# run show route advertising-protocol bgp 211a:978a:2:21::1de:1

    inet6.0: 50634 destinations, 50634 routes (50634 active, 0 holddown, 0 hidden)
    Prefix Nexthop MED Lclpref AS path
    * 3a05:d840::/29 Self I
    * 3a05:d840:26::/48 Self I

     

    Any ideas what could be causing this?

     

    I have the bogon listing that is automated rejects from the Cymru guys, but I cannot see anything wrong there....

     

    Thanks

     

     



  • 2.  RE: Weird "reject" on MX240 Core router
    Best Answer

    Posted 08-17-2018 02:22

    Hi,

     

    3a05:d840::/29 route is showing as aggregate route. By default, the next-hop type of aggregate route is "reject"

    Please check if you have configured any aggregate route

     



  • 3.  RE: Weird "reject" on MX240 Core router

     
    Posted 08-17-2018 02:29

    Yep, Certainly have:

     

    set routing-options rib inet6.0 aggregate route 3a05:d840::/29 policy aggregate-route-ipv6

    set policy-options policy-statement aggregate-route-ipv6 from protocol direct
    set policy-options policy-statement aggregate-route-ipv6 from route-filter 3a05:d840:26::/48 orlonger
    set policy-options policy-statement aggregate-route-ipv6 from route-filter 3a05:d840::/29 orlonger

     

    Aggregates have to advertised upstream. Would this affect routes back? It does not seem to affect a route back to the LNS DSL Customers as they are working with IPv6 in that prefix range (3a05:d840::/29).....

     

    After a quick check, it does indeed cause an issue as a traceroute show "no route to host" as it will with a reject.

     

    Thanks

     

     



  • 4.  RE: Weird "reject" on MX240 Core router

    Posted 08-17-2018 02:51

    Hi,

     

    Which IP and from where you are tracing? If there is no specific route for traced IP in MX routing-table, it will match the aggregate route and will reject the packets and send the ICMP Destination network unreachable response to client. This is an expected behaviour. 

     



  • 5.  RE: Weird "reject" on MX240 Core router

     
    Posted 08-17-2018 02:53

    All is cool. 

     

    I don't think the "reject" actual stops anything working unless you try and do something direct from the MX240 Core router itself.

     

    An example would be as follows:

     

    CPE has address 3a05:d840:ff45:0060::1 - this falls within the prefix and ALSO shows as reject on the core. However, if I perform a ping and traceroute to facbooks IPv6 address, it all works fine. So, I think the "reject" on the core is a red herring.

     

    I will close this. Thanks for the advice regarding the aggregate route....