BGP prefers Origin IGP vs INCOMPLETE. But for what?

[Evgeniy Ivanov]

Hi!
Can anyone explain practical aspect of using "Origin" attribute in BGP path selection.
As i know, this rule states that:
- prefer IGP routes. That means that this routes was inserted to BGP via

network

command.
- then prefer EGP routes. It is not useful now, since EGP is dead.
- then prefer INCOMPLETE routers. That means that this routes was inserted to BGP via

redistribute

command.
In other words, we can say that this rule now means that:
BGP will prefer routes originated by

network

command versus  routes originated by

redistribute

command.

What is purpose of this check?

[vivek srivastava · Accepted solution]

Hi,

Purpose is to validate the routes which are best to go with.

1. If anyone has advertised the routes via

network

command means that he has more control over what he is advertising. Also it meas that those routes belongs to him.

2. with redistribution, we practically has less control. In most cases redistributed routes are came from other adminitration domain and we are using route-maps etc to control them.

So if you have to choose over one another, what will you do ??

Same way BGP does, it preferes routes advertised via

network

command over redistribution bcause of its more valid and under control.

Vivek

[Evgeniy Ivanov]

Vivek, thanks!