What does Null0 mean?

A null interface is a virtual interface that discards IP packets and is used to prevent routing loops from occurring in the network. You do not assign the null interface an IP address. Instead, you create a static route for a network and set the next hop to the null interface (null0).

What is Null0 used for?

Introduction. The Null interface is typically used for preventing routing loops. Enhanced Interior Gateway Routing Protocol (EIGRP), for instance, always creates a route to the Null0 interface when it summarizes a group of routes.

What is IP Blackhole?

The most common form of black hole is simply an IP address that specifies a host machine that is not running or an address to which no host has been assigned. Even though TCP/IP provides a means of communicating the delivery failure back to the sender via ICMP, traffic destined for such addresses is often just dropped.

How does a summary route to null0 work?

In conclusion, a summarized route to Null0 interface is created along with the summarization of that route. If the summarizing router does not have a specific route for a subnet of that summarized route, it will send packets to Null0, sometimes called a “black hole”. This helps prevent routing loop and reduce unnecessary traffic.

What’s the prupose of ” IP route null0 “?

The purpose of configuring a static summary route to null0 is to make sure that traffic will be dropped on the local router if a more specific route doesn’t exist. 11-23-2005 10:29 AM 11-23-2005 10:29 AM Re: What’s the prupose of “ip route null0”? Oh, and yes it would show up in the output of the show ip route. 11-23-2005 10:28 AM

Why do I need a NULL 0 route?

One of those reasons has to do with route summarization. Essentially configuring the null 0 route is to provide protection from “black hole” developing. An example might help. Lets assume that a network is using subnets of 172.17.0.0.

Why does auto summarize send packets to null0?

If the summarizing router does not have a specific route for a subnet of that summarized route, it will send packets to Null0, sometimes called a “black hole”. This helps prevent routing loop and reduce unnecessary traffic. We can summarize a route via auto or manual summarization.