Limiting the Number of Advertised IS-IS Areas
By default, IS-IS advertises a maximum of three areas in the IS-IS hello (IIH) PDUs and link-state PDUs. To advertise more than three ISO network addresses for a router, include the max-areas statement:
The range that you can configure is from 3 through 36, and the default is 3. This value is included in the Maximum Address Area field of the IS-IS common PDU header included in all outgoing PDUs.
 | Note: The maximum number areas you can advertise is restricted to 36 to ensure that the IIH PDUs have enough space to include other type, length, and value (TLV) fields, such as the Authentication and IPv4 and IPv6 Interface Address TLVs. |
For a list of hierarchy levels at which you an configure this statement, see the statement summary section for this statement.
