bgp originate attribute

[sachin30720041]

Hello,

I am trying to understand the BGP originate attribute. Can anyone give an example where the BGP originate attribute is preferred over the AS-PATH attribute?

Thanks

[balaji.bandi]

Origin - How BGP learned of this network. i = by network command, e = from EGP, ? = redistributed from other source. Well-known, mandatory.
AS path - An ordered list of all the autonomous systems through which this update has passed. Well-known, mandatory.

here is the path selection BGP works ( there is some exmaple output posted there)

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html

[sachin30720041]

Thanks for responding.

In the document, 3rd point is prefer the path distributed through network command and the 5th point is prefer the path with the lowest origin type(IGP>EGP>incomplete)

3. 'Prefer the path that was locally originated via a network or aggregate BGP subcommand or through redistribution from an IGP.'

5. Prefer the path with the lowest origin type.

But all the prefixes distributed through network command have IGP origin type. So aren't  3rd and 5th points the same?

Thanks,

Sachin

[Harold Ritter · Accepted solution]

Hi @sachin30720041 ,

> But all the prefixes distributed through network command have IGP origin type. So aren't  3rd and 5th points the same?

Point number 3 is for locally originated prefixes. If the prefix is locally originated it will be preferred over other prefixes that are not locally originated, regardless the origine (IGP/EGP/Imcomplete).

Regards,

[balaji.bandi]

Difference is 

3. Prefer the path that was locally originated via a network.

5. Prefer the path with the lowest origin type. 

so always local preferred right.

[Lazarus_telecomTech]

Take a look at this video that helps to illustrate how the Originate or the Self-Origination BGP attribute operates:

https://youtu.be/xa9OfO6i1_M?si=YDU0IX4sqkOuX1eM