Unable to diagnose L2TP tunnels and run OSPF

Hello!

I have an odd problem with L2TP server over IPSEC on my FG-100F box running 7.4.6 software.

My configuration:

config vpn ipsec phase1-interface edit "L2TP-VOLZ" set type dynamic set interface "VLAN96-TESTLAB" set ike-version 2 set peertype any set net-device enable set proposal aes256-sha512 set dpd on-idle set psksecret ENC <removed> set dpd-retryinterval 60 next end  config vpn ipsec phase2-interface edit "L2TP-VOLZ" set phase1name "L2TP-VOLZ" set proposal aes256gcm set encapsulation transport-mode set l2tp enable next end  config vpn l2tp set status enable set eip 10.100.251.254 set sip 10.100.251.1 set enforce-ipsec enable set usrgrp "IPSEC VPN" end  config system interface edit "l2t.TESTLAB" set vdom "TESTLAB" set allowaccess ping set type tunnel set snmp-index 99 next end  config system interface edit "L2TP-VOLZ" set vdom "TESTLAB" set ip 0.0.0.0 255.255.255.255 set allowaccess ping set type tunnel set snmp-index 129 set interface "VLAN96-TESTLAB" next end   config router static edit 4 set dst 10.100.251.0 255.255.255.0 set device "l2t.TESTLAB" next end

Remote router connects successfully, it gets IP address 10.100.251.2 on its side.
But there is some issues.

1. It looks like Fortigate allocates 10.100.251.1 on its side, but it seems that it is not bound to any interface:

gw-fond-2 (TESTLAB) # diag ip address list | grep 10.100.251.1

-- empty output.

2. As a result, customer is not able to ping 10.100.251.1, and Fortigate is not able to ping customer as well:

gw-fond-2 (TESTLAB) # execute ping-options source 10.100.251.1  gw-fond-2 (TESTLAB) # execute ping 10.100.251.2 PING 10.100.251.2 (10.100.251.2): 56 data bytes  --- 10.100.251.2 ping statistics --- 5 packets transmitted, 0 packets received, 100% packet loss

3. L2TP VPN diagnostic commands both return empty outputs:

gw-fond-2 (TESTLAB) # diag vpn l2tp status

-- empty

gw-fond-2 (TESTLAB) # diag vpn l2tp tunnel

-- empty.

4. OSPF is not able to run over L2TP tunnels because it does not see any interfaces.

What am I doing wrong? Thanks!