Redistribute static Route with Null0

MinaryMinary Member Posts: 74 ■■□□□□□□□□
I have searched around and can't find a clear and authortative answer to why Null0 is used here so a default route is generated to downstream devices:

router eigrp 200
redistribute static
ip route Null0

I have seen some explainations but I don't want to cloud the thread if someone has a better answer.

thanks !


  • EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    Null0 is the discard path. It's normally used for summary routes, to prevent loops. Lets say RA had a default route pointing to RB, RA had 10 networks, -> locally. You create a summary which gets advertised to RB, lets say network fails, the summary is still advertised to B. Traffic coming form B to will arrive on RA, since is down, traffic will take the default route to RB and you have a loop. So when you config a summary a null route is placed in the global rib.

    Now say i want to advertise a default route, i first need to have it in my routing table, so as per above you need a static route, which will then be redistributed. If i point the static at an interface, that means all unmatched traffic will exit that interface, maybe i don't want that to happen. I want unknown traffic to get dropped, that's when i use a default to Null0.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
  • MinaryMinary Member Posts: 74 ■■□□□□□□□□
    That is a great explaination. Thanks.
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