Hi, everybody!
We have next scheme:
Cisco IP Phone connected to the Cisco Catalyst 2960 by access port (with voice and data vlans).
Cisco Catalyst 2960 connected to the Juniper EX4200 by trunk port (include data and voice vlan).
Juniper EX4200 (with RVI for data and voice vlans) configured as bootp helper for the devices connected to access and voice vlans.
According to the scheme above, the phones can not obtain the IP-address.
Otherwise another devices (not IP-phones) connected to Cisco Catalyst can obtain IP-address in data vlan and separately in voice vlan (configured as data vlan on port).
And if IP-phones connect directly to Juniper EX4200 (with access port with voice vlan + lldp + lldp-med), then IP-phones also can obtain IP-address.
And another scheme with Cisco Catalyst 2960 + Cisco Catalyst 3850 (with configured RVI and bootp helper) instead Juniper EX4200, IP-phones also can obtain IP-address.
What coulde be the problem with obtain IP address in voice vlan through Cisco Catalyst + Juniper EX trunk?
(dhcp request from IP-phone in attachment. wireshark screen)