Null interface eigrp

It is often use in large networks with many subnets because it reduces the number of routes that a router must maintain and minimizes the traffic used for routing updates. Finally, What is a Null0 route? A null interface is a virtual interface that discards IP packets and is used to prevent routing loops from occurring in the network. Null0 is a virtual interface that is a route to nowhere and is used to prevent routing loops for destinations that are included in a summary network but do not have a specific entry in the routing table.

Static routing is a form of routing that occurs when a router uses a manually-configured routing entry, rather than information from dynamic routing traffic.

In many cases, static routes are manually configured by a network administrator by adding in entries into a routing table, though this may not always be the case. Route Summarization Overview. This command lets you specify a summary address for routes advertised through a specific interface by EIGRP.

Note: There may be situations where the use of a summary static route to Null0 is not feasible. For example, if in the previous example:. Note: The result would be that packets in transit or applications that attempt to reach this block of IP addresses create the same routing loop described earlier.

Note: To fix this routing loop, you must use the ip route The in the command is the administrative distance. Refer to What Is Administrative Distance? Note: Because we use a higher administrative distance than any routing protocol, if the route to Skip to content Skip to search Skip to footer. Available Languages. Download Options. Updated: January 7, Contents Introduction. Introduction The Null interface is typically used for preventing routing loops.

Prerequisites Requirements There are no specific prerequisites for this document. Command Syntax A static route to Null0 is a normal static route, except that it points to the Null0 interface, which is a virtual IOS interface.

The null interface provides an alternative method of filtering traffic. You can avoid the overhead involved with using access lists by directing undesired network traffic to the null interface.

Whenever a routing protocol summarizes, this means that the router might receive traffic for any IP address within that summary. Because not all IP addresses are always in use, there is a risk of looping packets in case default routes are used on the router which receives the traffic for the summary.

R1 configure terminal Enter configuration commands, one per line. R1 config interface null0 R1 config-if ip unreachable R1 config-if end R1. R1 config ip route 0. To Verifies the configuration of the null interface use "show interface null0" command.

Configure a Null Interface. Buy or Renew. Find A Community. Cisco Community. Thank you for your support! We're happy to announce that we met our goal for the Community Helping Community campaign! Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

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