as-path-expand vs as-path-prepend

[antonio.guirado]

Hello,

I'd like to know if Cisco has a similar command to "AS PATH EXPAND" in Juniper. If you see the juniper documentation:

You can expand or add one or more AS numbers to an AS sequence. The AS numbers are added before the local AS number has been added to the path.

It would be something similar to an as-prepend but insert the new AS numbers before the local as not after it as as-prepend do.

Thanks.

[ajay chauhan]

It does the same thing .

on juniper  it would be like.

policy-statement as-path-expand {

term expand {

            from {

               
                route-filter < Prefix > orlonger;

            }

            then as-path-expand last-as count < number >;

Ex- Prefix 10.0.0.0/8 and count 2

Remote router will get AS path prepended by 2.

on cisco it would be like.

route-map prepend permit 10

set as-path prepend

Thanks

[antonio.guirado]

No,

the as-prepend function inserts after the local AS. So the BGP neigbor see your prefixes with the AS PATH:

What as-path-expand does in a Juniper is insert the AS number before de local AS. So the neighbor sees the following AS PATH

The issue is that we want use only a BGP session to anounce prefixes for a private AS and prefixes for a public AS.

The AS origin should change depend on prefixes (using on prefix-list).

[Kishore Chennupati]

Hi Antonio,

If I am not mistaken you are enquiring about AS path appending not prepending in cisco world. umm. You can try using  the set as-path prepend last-as. This prepends the first AS in the AS-path (neighbor’s AS). You can use this command in an inbound route-map to simplify your configuration and make the route-map independent of the neighbor’s AS number.

However, if you are actually asking about appending the AS in a outbound route-map. I am not sure if you could do that on cisco devices.

HTH

Regards

Kishore

[antonio.guirado]

Yes I need appending the AS in a outbound BGP policy.

Thanks any way.