Problem With Firewall FortiGate 90D, Causes our voip systems to crash

[support_voxia]

Hello fortinent support, we have FortiGate 90D as our firewall for our voip systems.

Since we have installed it, we experience network issues that cause real problems on our asterisk based voip systems.

Turns out that something else in our network that is taking over your systems's IPs, and seems like a routing problem that its been caused from the firewall.

We see two symptoms for this:

1 - Every week or so one of the VPSes is disconnecting calls after 6 seconds - we see a system notification and arp that shows something else in the network is using the IP of the relevant VPS.

WARNING[19218]: chan_sip.c:3824 retrans_pkt: Retransmission timeout reached on transmission 805816439_92794992@82..166.66..147 for seqno 30155 (Critical Response) -- See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions Packet timed out after 6400ms with no response [Mar 1 15:18:39] WARNING[19218]: chan_sip.c:3853 retrans_pkt: Hanging up call 805816439_92794992@82.166.66.147 - no reply to our critical packet (see https://wiki.asterisk..org/wiki/display/AST/SIP+Retransmissions). -- User disconnected  

2 - we see in monitor of VPSes behind this FW that some extensions are registered with the Gatreway IP (199.203.181.241) - see print screen:

      MonitorTransferHangupReboot  No refresh 1 sec 3 sec 5 sec 10 sec 15 sec 20 sec 25 sec 30 sec 35 sec 40 sec 45 sec 50 sec 55 sec 1 min  ALL SIP  ALL Online Offline  ALL J  NameExtensionIP addressStatusUser-AgentOn Call501SIP/50182.81.8.7:1027 OnlineYealink SIP-T19P 31.72.18.3  502SIP/50282.81.8.7:1028 OnlineYealink SIP-T19P 31.72.18.3  503SIP/50382.81.8.7:1030 OnlineYealink SIP-T19P 31.72.18.3  504SIP/50482.81.8.7:1026 OnlineYealink SIP-T19P 31.72.18.3  505SIP/50582.81.8.7:1029 OnlineYealink SIP-T19P 31.72.18.3  506SIP/50682.81.8.7:1025 OnlineYealink SIP-T19P 31.72.18.3  JennySIP/500199.203.181.241:60537 OnlineYealink SIP-T19P 31.72.18.3