OSPF area notation
OSPF is able to use either a decimal number or a dotted notation to indicate the area. For example both of the following commands have identical results:
R2(config-router)#network 192.168.23.0 0.0.0.255 area 5 R2(config-router)#network 192.168.23.0 0.0.0.255 area 0.0.0.5
The router interprets both of these in binary anyway, so they are the same.
Notice the following:
<0-4294967295> OSPF area ID as a decimal value A.B.C.D OSPF area ID in IP address format
The range of values in decimal is the same as the number of values in a 32 bit dotted decimal notation.