Sorry for the delayed reply. Here is my config on the inter-connected AS2 router.
Let me preface that again, I am not sure if this is the best way to accomplish this. I take it that there is probably several ways to solve this ...
add address-families=ip as-override=no default-originate=never disabled=no hold-time=3m in-filter="" instance=default multihop=no name=\
ibr1.gpt1 nexthop-choice=default out-filter=BGP-OUT-1 passive=no remote-address=172.29.0.2 remote-as=1 remove-private-as=no \
route-reflect=no tcp-md5-key="" ttl=default update-source=172.29.0.1 use-bfd=no
add address-families=ip as-override=no default-originate=never disabled=no hold-time=3m in-filter="" instance=default multihop=no name=\
ibr1.mob2 nexthop-choice=default out-filter=BGP-OUT-3 passive=no remote-address=172.29.0.6 remote-as=3 remove-private-as=no \
route-reflect=no tcp-md5-key="" ttl=default update-source=172.29.0.5 use-bfd=no
add advertise-filter=BGP-OUT-3 attribute-filter="" disabled=no include-igp=no inherit-attributes=yes instance=default prefix=\
subnet.from.as1.0/24 summary-only=yes suppress-filter=""
add advertise-filter=BGP-OUT-1 attribute-filter="" disabled=no include-igp=no inherit-attributes=yes instance=default prefix=\
subnet.from.as3.0/24 summary-only=yes suppress-filter=""