Routing to NBMA Interfaces

Hey everyone,

Working through the v5 Workbook, and I'm on "Routing to NBMA Interfaces".

Just wondering, if anyone could clarify the difference (if any) between using the following set of commands:


Option 1:

ip route Tunnel0


Option 2:

track 1 interface Tunnel0 line-protocol

ip route track 1


The solution uses Option 1, but my brain just automatically went to Option 2... Am I totally wrong?


  • Hi,

    For clarity, this is what the task says : 

    • Configure R1 and R2 with IPv4 default routes through the DMVPN cloud with a next-hop of R5.
      • Ensure that the route is valid as long as the Tunnel interface is in the UP state.
    The task is trying to outline the different ways static routes can be implemented, that's why the solution guide used option 1 from your example. Both solutions accomplish the same thing, default route with a next hop of, the difference being how the next-hop validity is being verified.

    Option 1 outlines that the outgoing interface is Tunnel0 and since the interface is multipoint, then the exact next hop must be statically set, while if the interface was a point-to-point interface, IP address wouldn't have been necessary.


    interface Tunnel0

     ip address

     ip mtu 1400

     ip nhrp authentication NHRPPASS

     ip nhrp map

     ip nhrp map multicast

     ip nhrp network-id 1 

     ip nhrp holdtime 300

     ip nhrp nhs

     ip tcp adjust-mss 1360

     tunnel source GigabitEthernet1.100

     tunnel mode gre multipoint

     tunnel key 150

     tunnel protection ipsec profile DMVPN_PROFILE 

    Option 2 suggested by you validates next hop by using enhanced object tracking which is also fine when talking about functionality.

    Remember that the lab exam is different, the functionality is what the task will be looking for, not the way the tasked has been implemented. For example, in this case, shutting R1's interface Tunnel0 should lead to not having the default route in the routing table.

  • Really Helpful Romania :) Thanks a lot

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