USG at branches of routed IPsec via vti interfaces with BGP not working in fully symmetrical manner

ohornig Posts: 2
First Comment
edited April 2021 in Security


I am here to deal with a bit strange problem. I have configured IPsec VPN between Fortinet Fortigate acting as a VPN hub with public IP address, and USG20-VPN as a hidden branch witch only a private IP address.

I used verified configuration on Fortigate side (Dial-Up IPsec with addressed interface) and started to play with IPsec parameters on USG side. I configured VPN Gateway, VPN connection, VTI Interface, BGP and also a Policy route. Tunnel is up and running.

BGP routes are exchanges between VTI at USG and tunnel interface at Fortigate. VTI of USG is not pingable from Fortigate, but Fortigate interface is pingable from USG.

I am able to ping server at HQ (Fortigate side) from computer at branch (USG side), so the connection estabilished from branch side is working properly (also RDP and other protocols are working). But I am not able to ping from HQ to branch - connection initiated from HQ is not working.

After a few days of searching over, playing with parameters and reconfiguring number of setups (also policy based variant behaves in the same way) I am at the end of ideas.

Is there something that I miss?

Thanks anybody for reply.

All Replies

  • Zyxel_Jerry
    Zyxel_Jerry Posts: 1,073  Zyxel Employee
    First Anniversary 10 Comments Friend Collector First Answer

    Hi @ohornig

    Can you trace packet on VTI interface when try to ping from Fortigate to see if there is any request coming from Fotigate?

    Here is the steps to trace packet on USG.

    SSH into USG and type command below to trace the packet from fortigate.

    Router> packet-trace interface vti1(Vti interface name) ip-proto icmp

    And try to see if there is any packet coming from fortigate

    Here is the example

  • ohornig
    ohornig Posts: 2
    First Comment

    Hi Jerry,

    thank you for your response, it is helpful.

    I see in packet-trace:

    • outgoing ICMP, if I ping from branch
    • outgoing and incoming BGP exchanges between tunnel ends

    No incoming traffic.

Security Highlight