RFC 2328 and RFC 1583 each define a route selection rule differently. After OSPF is enabled on a switch, you need to specify a route selection rule based on the switch configuration. By default, a switch complies with the route selection rule defined in RFC 1583. If the neighboring switch complies with the route selection rule defined in RFC 2328, you need to configure the local switch to comply with that defined in RFC 2328. This allows all switches in an OSPF area to comply with the same route selection rule.