The origin as-path attribute describes where a router received the route from. Origin information for each route MUST be transmitted in every BGP Update message as it is a well-known mandatory attribute. This means that ALL implementations of BGP must support it and pass it on when sending routing information.
The origin attribute can contain one of three values:
- Internal
- External
- Incomplete
INTERNAL
The route was inserted into BGP via the interior routing protocol.
EXTERNAL
The route was received from an external BGP peer (eBGP peer). The route is external to the local network.
INCOMPLETE
The router isn't quite sure the route is actually correct, but it comes from the local protocol and was inserted automatically from a static route using the redistribute command. Despite what most NOC technicians seem to believe, this is NOT an invalid route. Most customers redistributing their static routes into their BGP tables will have incomplete routes. All incomplete really means is that there was no origin information passed to the router when it learned the route. Such would always be the case with a redistributed static route.
I've had more than one NOC 'expert' tell me that 'incomplete' means I'm not advertising the route which is just plain WRONG. --InetDaemon