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  1. Hi Rob,

    There’s a big difference between the two. An EIGRP router that is configured as a stub does not receive queries when one of its neighbors loses a network.

    Passive-interface is about sending hello packets on an interface. Normally when you use the network command to advertise something then it does two things:

    1. It advertises all networks that fall within the range of your network commmand on all active interfaces.
    2. It sends hello packets on all active interfaces that have networks that fall within the range of your network command.

    When you enable passive-interface, it will stop sending the hello packets. This is useful on interfaces that connect to end-devices like phones, workstations, servers, etc. You probably don’t want to send EIGRP hello’s in their direction…there are no EIGRP routers there.

    Hope this helps!

    Rene

  2. Hi,

    Yes this is pretty much exactly what I said in my post.

    There are some specific use cases where you will need to allow a stub router to process queries (such as multihomed branch offices in a DMVPN deployment where if R1’s uplink fails, you have to reconverge through R2 etc).

  3. Hello Jeremy

    This is a great question and it brings up some subtle points of how EIGRP functions. Queries are subject to the split horizon rule just like advertisements are. If you get a query for a network from an interface, you never send out a query for that same network from that interface.

    So in the first case, when R2 lost connectivity to the loopback network, it sent a query to R1 for an alternate route to that destination. This is because in this case, R1 is not a stub. Because R1 got a query from R2, it did not send a query back to R2 via that interface due to the split horizon rule.

    Now in the second case R2 knows that R1 is a stub so it doesn’t sent a query for the lost network. When R1 learns of the lost connectivity to the network (via updates etc), it hasn’t received a query for that network, so it can send a query to R2 without breaking the split horizon rule.

    I hope this has been helpful!

    Laz

  4. Thank you Lazaros,
    It is clear for me, and I have to say that I am one of the luckiest person that I have Lazaros.

  5. Hello Rene,

    I took some time to lab this “eigrp stub redistributed” out and found some interesting parts (if only “redistributed” is in it without “connected” and “summary”)
    The Stub router will only advertise if you use the eigrp “redistribute” command with an foreign routing protocol or another EIGRP AS it wont advertise the route if you use “redistribute connected” or “redistribute static” you need to manually type “stub connected redistributed static” to do that.

    Update: I just did a “show version” and it’s IOS release 12.4

    Best regards,
    Marcel

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