FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article explains how to configure area number greater than 255 on the FortiGate OSPF setting to match that of Cisco.
The area ID in OSPF is represented in a dotted decimal format, similar to an IP address. While Cisco routers allow a single decimal value for configuring area, a FortiGate requires the area to be configured in a dotted decimal format.
FortiOS 4.0, 5.0, 5.2
The decimal area that is configured on the Cisco will have to be converted into a dotted decimal format and then used on the FortiGate.
Area number configured on the Cisco 256 Corresponding dotted decimal format for FortiGate is: 0.0.1.0
Area number configured on Cisco 257 Corresponding dotted decimal format for FortiGate is: 0.0.1.1
Using the sniffer:
The other way, in case you do not want a conversion would be to run a sniffer on proto 89 and look at the OSPF header. The command is:
diagnose sniffer packet "proto 89" 6 0 a
Once the packets are captured, convert it using help from the related KB article 'How to import Diag Sniff Packet data to WireShark - Ethereal application'.