Displaying configuration of a single interface can be a time-consuming task if your router has extremely long configuration (for example, high-end device with hundreds of interfaces, route-maps, access-lists etc.). In this case, the interface keyword of the show running-config command becomes extremely useful.
For example, the show running-config interface serial 0/0.1 command displays only configuration of the specified interface (without building the whole running configuration)
POP#show running-config interface serial 0/0.1 Building configuration... Current configuration : 154 bytes ! interface Serial0/0.1 point-to-point description *** Link to Core-1 *** ip address 172.16.1.6 255.255.255.252 frame-relay interface-dlci 101 end