What Is The Purpose Of A Null0 Route In The Routing Table?
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What is the purpose of a Null0 route in the routing table?
Answer: The EIGRP of IPv4 install the Null0 route in the routing table automatically during the enabled time of EIGRP summarization and at least one of the EIGRP learned subnet is present.it is basically the interface with no route and works by preventing the routing loops from the destination which is the part of the summary network but has no specified entry in a routing table.
Configuration of the Null0 interface
When the static route configuration occurs through the Null0 interface, then the frames drop without the configuration of an ACLs to the blocked traffic or any ICMP message. That kind of interface is not available to receive or move further any kind of traffic and the encapsulation of any kind will fail.
The null interface gave the method to filter the traffic you are able to escape the overhead included with the help of ACLs by directing the unwanted network traffic to the interface. The interface work by preventing the routing loops, EIGRP formed the route toward the null0 interface during the group of route summarization. The summarization of the routing protocol indicates that may be the router receive the traffic for any kind of IP address from the summary because not all IP address is used always a risk factor involved for the looping packets if the default route is used in some case on the router which is assigned to receive the traffic form summary.
The summary route is created by the ABR and ASBR when the configuration of OSPF summarization occurs but they are not real routes, but it points toward the Null0 interface which is also known as the discard interface.
R1#configure terminal
R1(config)#interface null0.
R1(config-if) #ip unreachable.