What Does Area Border Router (ABR) Mean?
An area border router (ABR) is a kind of router that is located near the border between one or more Open Shortest Path First (OSPF) areas. It is used to establish a connection between backbone networks and the OSPF areas. It is a member of both the main backbone network and the specific areas to which it connects, so it stores and maintains separate routing information or routing tables regarding the backbone and the topologies of the area to which it is connected.
Techopedia Explains Area Border Router (ABR)
As the name implies, this router is found on the border of each OSPF area, making it the arrival and departure point that distributed information needs to pass through in order to connect to other areas or to the backbone itself.
When arriving, there is a designated route provided by the ABR to move traffic from other areas. When exiting, there is a need for the local area’s ABR to be able to reach a certain destination for the routing information. The main function of ABRs is to summarize sub networks found throughout the OSPF system. It stores many copies of its link-state database in memory when one of the stored copies shows an area where the actual router is connected.