Cisco Notepad

OSPF area capability transit is enabled by default, allowing the OSPF Area Border Router to install better-cost routes to the backbone area through the transit area instead of the virtual links.

If you want to retain a traffic pattern through the virtual-link path, you can disable capability transit by entering the no capability transit command. If paths through the transit area are discovered, they are most likely to be more optimal paths, or at least equal to, the virtual-link path. To reenable capability transit, enter the capability transit command.

If you need to verify whether OSPF area capability transit is enabled for a specific routing process, enter the show ip ospf command.

DOC CD Navigation

• Cisco IOS IP Routing Protocols Configuration Guide, Release 12.4
• Part 5: OSPF
• OSPF Area Transit Capability

Also we can look up in the Command Reference.