Setting up a cisco remote ip phone through a vpn tunnel?

Question

VPN

Hello!
Faced a problem
There is an l2tp tunnel based on mikrotik. Version up to 6.35.4. On the one hand (network 1) there is ip telephony based on cisco, on the other side (network 2) ip cisco phone.
Routing is configured correctly, on the one hand, it sees network 2, on the other hand, network 1. The firewall does not block ports. The essence of the problem is that a phone that is located on the side of network 2 cannot receive settings / connect to the tftp server. Option 66 and 150 on dchp in network 2 is configured but in the phone logs the connection attempt is not successful, who will tell you where to dig and what could be the problem?

Answer 1

And how do you specify option 66? As a string or as an ip address?