pls explain as-override feature in brief if possible please give me the example
neigh x.x.x.x as-override allows to a PE router to change the private ASN used by a CE node on an eBGP session running on a VRF access link.
the private ASN is changed in the PE ASN.
another CE node on another VRF (=connected to another PE node) will see the eBGP route coming from first site with an AS path of:
this allows to use the same private ASN on all sites of a customer.
That is a clear management advantage for a service provider.
This because BGP by default doesn't accept BGP routes with an AS path attribute that contains local AS number.
Hope to help