If you’ve ever had to configure OSPF on a Cisco router, you’re well familiar with the venerable network statement, which effectively assigns interfaces into OSPF areas based on their IP addresses. Although our life became simpler when the network statements stopped being order-dependent (the order dependency allowed for a few nasty surprises in the troubleshooting part of the CCIE lab when the CCIE title still implied you had to be able to fix other people’s mistakes :), it was still an awkward way of configuring what belongs where.

In IOS release 12.3(11)T (integrated in 12.4), Cisco finally implemented OSPF the way it should have been implemented 20 years ago - you configure the OSPF area on individual interfaces with the ip ospf process area area-id interface configuration command.

The network statements still work as expected, and the per-interface command overrides whatever the network statement would do, so you have an extremely nice combination that allows you to assign all interfaces into a particular area (for example, network 0.0.0.0 255.255.255.255 area 2) and change the area for only a few interfaces (for example, uplinks into the backbone area).