With BIRD 2.0.0 on the route server:

rs$ birdcl show route all
BIRD 2.0.0 ready.
Table master4:
1.0.1.0/24           unicast [AS10 17:33:32.159] * (100) [AS10i]
        via 192.0.2.10 on eth0
        Type: BGP univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100
        BGP.ext_community: (generic, 0x43000000, 0x1)
rs$ birdcl show route all export AS20
BIRD 2.0.0 ready.
Table master4:
1.0.1.0/24           unicast [AS10 17:33:32.159] * (100) [AS10i]
        via 192.0.2.10 on eth0
        Type: BGP univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100
        BGP.ext_community: (generic, 0x43000000, 0x1)

from the receiving client:

receiver$ birdcl show route all
BIRD 1.6.3 ready.
1.0.1.0/24         via 192.0.2.10 on eth0 [the_rs 17:33:32 from 192.0.2.2] * (100) [AS10i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100
        BGP.ext_community: (generic, 0x43000000, 0x1)




With BIRD 1.6.3 on the route server:

rs$ birdcl show route all
BIRD 1.6.3 ready.
1.0.1.0/24         via 192.0.2.10 on eth0 [AS10 17:36:56] * (100) [AS10i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100
        BGP.ext_community: (generic, 0x43000000, 0x1)
rs$ birdcl show route all export AS20
BIRD 1.6.3 ready.
1.0.1.0/24         via 192.0.2.10 on eth0 [AS10 17:36:56] * (100) [AS10i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100
        BGP.ext_community: (generic, 0x43000000, 0x1)

from the receiving client:

receiver$ birdcl show route all
BIRD 1.6.3 ready.
1.0.1.0/24         via 192.0.2.10 on eth0 [the_rs 17:36:56 from 192.0.2.2] * (100) [AS10i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 10
        BGP.next_hop: 192.0.2.10
        BGP.local_pref: 100