Use Lo0 as source ip address for BGP adjacency as shown below.
protocols {
bgp {
group interop {
type internal;
local-address 10.10.10.70;
family evpn {
signaling;
}
neighbor 10.10.10.26;
Remove vrf-import under switch-options and use the simple switch options command.
Example:
set policy-options policy-statement VRF-IMPORT term Vxlan10 from community vxlan10
set policy-options policy-statement VRF-IMPORT term Vxlan10 then accept
set policy-options community vxlan10 members target:777:777
set switch-options vtep-source-interface lo0.0
set switch-options route-distinguisher 1.1.1.1:100
set switch-options vrf-import VRF-IMPORT
set switch-options vrf-target target:777:777
set protocols evpn extended-vni-list 10
set protocols evpn multicast-mode ingress-replication
set protocols evpn vni-options vni 10
Repeat the same on other QFX5100 device. Remove policy configuration and use the above example. Ping should go through.