Editing Router (computing) (section)

== Operation ==
When multiple routers are used in interconnected networks, the routers can exchange information about destination addresses using a [[routing protocol]]. Each router builds up a [[routing table]], a list of routes, between two computer systems on the interconnected networks.<ref>{{cite web|title=Cisco Networking Academy's Introduction to Routing Dynamically|url=http://www.ciscopress.com/articles/article.asp?p=2180210&seqNum=4|publisher=Cisco|access-date=August 1, 2015|url-status=live|archive-url=https://web.archive.org/web/20151027133937/http://www.ciscopress.com/articles/article.asp?p=2180210&seqNum=4|archive-date=October 27, 2015}}</ref><ref name="Cisco 2022 u602">{{cite web | title=What Is Routing? | website=Cisco | date=2022-04-10 | url=https://www.cisco.com/c/en/us/products/routers/what-is-routing.html | access-date=2024-03-25| quote=
Routing tables can be created manually and "learned" by software as it observes network traffic, or they can be built according to [[routing protocols]].}}</ref>

The software that runs the router is composed of two functional processing units that operate simultaneously, called ''planes'':<ref>{{cite ietf |title=Requirements for Separation of IP Control and Forwarding |rfc=3654 |author=H. Khosravi & T. Anderson |date=November 2003}}</ref>
* [[Control plane]]: A router maintains a routing table that lists which route should be used to forward a data packet, and through which physical interface connection. It does this using internal pre-configured directives, called [[static route]]s, or by learning routes [[Dynamic routing|dynamically]] using a routing protocol. Static and dynamic routes are stored in the routing table. The control-plane logic then strips non-essential directives from the table and builds a [[forwarding information base]] (FIB) to be used by the forwarding plane.
* [[Forwarding plane]]: This unit forwards the data packets between incoming and outgoing interface connections. It reads the [[Header (computing)|header]] of each packet as it comes in, matches the destination to entries in the FIB supplied by the control plane, and directs the packet to the outgoing network specified in the FIB.