Configuring an OSPF backbone or normal area

Syntax:

area [[ospf-area-id] | [backbone]] [normal] [[ospf-area-id] | [backbone]]

After using router ospf to globally enable OSPF and enter the global OSPF context, execute this command to assign the routing switch to a backbone or other normal area.

The no form of the command removes the routing switch from the specified area.

Default: No areas; Range: 1 to16 areas (of all types)

ospf-area-id

Specifies a normal area to which you are assigning the routing switch. You can assign the routing switch to one or more areas, depending on the area in which you want each configured VLAN or subnet to reside.

You can enter area IDs in either whole number or dotted decimal format. (The routing switch automatically converts whole numbers to the dotted decimal format.)

For example, if you enter an area-ID of 1, it appears in the switch's configuration as 0.0.0.1 and an area-ID of 256 appears in the switch configuration as 0.0.1.0.

An area ID can be a value selected to match the IP address of a VLAN belonging to the area or a value corresponding to a numbering system you devise for the areas in a given autonomous system (AS.)

Entering an area ID of 0 or 0.0.0.0 automatically joins the routing switch to the backbone area.

The maximum area ID value is 255.255.255.254 (4,294,967,294.)

backbone

Assigns the routing switch to the backbone area and automatically assigns an area ID of0.0.0.0 and an area type of normal.

Using 0 or 0.0.0.0 with the above ospf-area-id option achieves the same result. The backbone area is automatically configured as a normal area type.

Example

To configure a backbone and a normal area with an ID of "1" (0.0.0.1) on a routing switch:

switch(ospf)# area backbone 
switch(ospf)# area 1