VXLAN on DCI question

Hi

I have been setting up my QFX5100 IP fabric following this blog:

lab-on-evpn-vxlan-on-juniper-qfx5100-switches

inside my fabric all works well.

I then setup another fabric pod using the same methodology.

when I link the two pods together via a direct fibre link, I run the underlay as eBGP to share the leaf switches loopbacks.

this is all good.  I can see all local leafs and all remote leafs and can ping between them.

I then run an eBGP overlay for EVPN signalling.

everything looks ok ,

sniffing inside the POD I am seeing VXLAN traffic but sniffing on the inter POD link I am seeing non VXLAN traffic.

BGP config is such:

show configuration protocols bgp 
log-updown;
graceful-restart;
group underlay {
    type external;
    mtu-discovery;
    family inet {
        unicast;
    }
    export bgp-underlay-out;
    bfd-liveness-detection {
        minimum-interval 350;
        multiplier 3;
        session-mode single-hop;
    }
    multipath multiple-as;
    //spine switch
    neighbor 10.133.0.0 {
        peer-as 64600;
    }
    //spaine switch
    neighbor 10.133.0.2 {
        peer-as 64601;
    }
    //leaf in remote POD
    neighbor 10.200.1.1 {
        peer-as 65101;
    }
}
group overlay {
    type external;
    multihop {
        ttl 255;
    }
    local-address 10.100.110.3;
    family evpn {
        signaling;
    }
    //local leaf
    neighbor 10.100.110.4 {
        peer-as 65002;
    }
    //local leaf
    neighbor 10.100.110.5 {
        peer-as 65003;
    }
    //local leaf
    neighbor 10.100.110.6 {
        peer-as 65004;
    }          
    //leaf loopback in remote POD                         
    neighbor 10.100.110.22 {
        accept-remote-nexthop;
        peer-as 65101;
    }
}

My underlay is using an eBGP session to each spine switch in the local pod and to the remotely connected leaf.

My overlay has an eBGP session to each local leaf loopback and to the loopback of the remotely connected leaf.

as these are eBGP sessions, I am expected to recieve the EVPN BGP traffic through this eBGP peer and it to set itself as the nexthop.

I believe the problem lies with the overlay eBGP setup and some config that I must be missing.

because:

when I make the leaf switches have eBGP sessions against all LOCAL and all REMOTE leaf switches everything works correctly, ie I get VXLAN traffic over my inter POD link.

I dont believe patch to be a scalable solution though.  I would have thought that as long as all local leafs have an eBGP session against the leaf that has the external eBGP link , things would work.....

any ideas?