Hi guys,

We are using BGP on RouterOS 5/6 and have a 32 AS number, but a new peer only supports 16 bit AS numbers.

I am aware that we should be able to deal with this using the AS_TRANS number as a 16 bit placeholder, but I don't know if RouterOS supports that.

Does anyone know? Is there any configuration that needs to be done?

Thanks.

Nothing needs to be done. Configure your router with your 4-byte ASN. Your peer will configure the session toward you with remote-as=23456. You will use their regular AS in remote-as=. BGP will bring up the session, and your upstream will see your AS as the 4-byte transitional ASN. The rest of the world which support 4-byte ASN's will see your real ASN in the path.

You will have no problem with 16-bit AS I personally use to peer 16bit 32Bit