Bgp why null0

I think that makes sense!! Thank you Rene. Hope this helps! Question about MPLS vpnv4 prefix default advertisement. Because R1 has: ip route 1. Hi Adrian, With a static route like this, everything that matches 1. Hello Rene, I have seen some documents that they advertise a network in BGP without using mask like below: router bgp 1 network 1.

Regards, -Rouzbeh. If we are going to use: router bgp 1 network Thank you so much for the answer, now it is clear for me. Hi, How do I advertise public IP to a peer? The router only knows the Everything that ends up there will just be dropped.

The Null0 "interface" is a virtual bit-bucket. Meaning it's a trash can to route things to. There's automatically a Null0 route called a Discard Route created when you do a summary-address or area-range or things like that with routing protocols.

The idea behind this is that you are creating a summary address manually to tell other routers about. If you are therefore expecting to receive packets for anything within that summary range, what will your router do about it? Anything not matching more specific routes would get sent to the discard route and therefore destroyed in a flash of Null0 mayhem. Without the discard route, your router would be either trying to look things up or possibly sending to a default route 0.

You may also use Null0 as a destination in static routes if you would like particular packets to die a horrible death as well! Rafael A Couto Cabral. Sign up to join this community. The best answers are voted up and rise to the top.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Once you've done this you can enter the network statement for Null 0 is a virtual interface that's used to guarantee routes make it into the RIB; remember, routes must have a next-hop in order to make it into the RIB. Routing in general works off a route table which is a list of routes and the first matching route is what is used.

What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? Null 0 interface is used to discard traffic destinated to paritcular network. It also help to summarize network prefix as you said. It creates inconsistent routing when the network has discontiguous networks. Automatic summarization does not prevent convergence of the routing table nor does it increase the size of routing updates. Fill in the blank. When a router has two or more paths to a destination with equal cost metrics, then the router forwards the packets using both paths equally.

This is called equal cost load balancing. The routing table contains the single destination network, but has multiple exit interfaces, one for each equal cost path. When a network enters the active state , DUAL must query neighbors for a new successor.

You also want the prefix to be advertised regardless if you are having some internal issues with routes flapping etc. Kind of like being a good net citizen. This is often called a pullup route. If you encounter a technical issue on the site, please open a support case.

Communities: Chinese Japanese Korean. All Rights Reserved. The Cisco Learning Network. Enterprise Certifications Community. View This Post. Edited by Admin February 16, at AM. BGP IP route null0. Dears , What the benefit of using ip route null0 command with bgp , I know that command will put the summary route for the subnet we need to advertised via bgp network command but what would be the point of all that if null0 means drop the packet?

Please can anyone explain this for me. I hope this has been informative for you! Sarmad, That only creates blackhole for traffic to a destination for which a router doesn't have a more specific address.