1/8/2024 0 Comments Fortigate loopback natTo provide the extra layer of encapsulation on IPsec packets, the Nat-traversal option must be enabled whenever a NAT unit exists between two FortiGate VPN peers or a FortiGate unit and a dial up client such as FortiClient. This extra encapsulation allows NAT units to change the port number without modifying the IPsec packet directly. When the Nat-traversal option is enabled, outbound encrypted packets are wrapped inside a UDP IP header that contains a port number. To work around this, the FortiGate provides a way to protect IPsec packet headers from NAT modifications. NAT cannot be performed on IPsec packets in ESP tunnel mode because the packets do not contain a port number.Īs a result, the packets cannot be de multiplexed. When an IP packet passes through a NAT unit, the source or destination address in the IP header is modified.įortiGate units support NAT version 1 (encapsulate on port 500 with non-IKE marker), version 3 (encapsulate on port 4500 with non-ESP marker), and compatible versions. Network Address Translation (NAT) is a way to convert private IP addresses to publicly routable Internet addresses and vice versa. Id=20085 trace_id=57 func=ipd_post_route_handler line=490 msg="out port3 vwl_zone_id 0, state2 0x1, quality 0." Related Document.This article discusses about the nat traversal options available under the phase 1 settings of an IPsec tunnel. Id=20085 trace_id=57 func=_ip_session_run_tuple line=3489 msg="SNAT 10.210.10.84->10.10.10.1:1" 5) Traffic is now being sent from FortiGATE firewall port 3 (LAN port) to user A IP: Id=20085 trace_id=57 func=_iprope_check_one_policy line=1941 msg="checked gnum-100004 policy-3, ret-matched, act-accept" 4) SNAT happened for user B source IP from SNAT IP pool 'SNAT': Id=20085 trace_id=57 func=init_ip_session_common line=5894 msg="allocate a new session-000ca471" 2) Routing lookup will happen for destination IP : 10.200.10.86 and it found a route to reach destination : 10.200.10.86via port 3 i.e. # diagnose debug enable 1) When user B : 10.210.10.84 behind vendor end firewall ping user A IP : 10.200.10.86, it get translated into dummy IP : 10.10.10.1 and user A will get ping request from 10.10.10.1 instead of actual IP of user by traffic first hit tunnel interface port AZ (FortiGate firewall tunnel interface) and allocate a new session. # diagnose debug flow filter saddr 10.210.10.84 Step by step traffic flow for TASK 2 solution: Id=20085 trace_id=61 func=_iprope_check_one_policy line=2159 msg="policy-2 is matched, act-accept" 5) Encrypted traffic will be sent out from fortigate firewall WAN interface port 1. Id=20085 trace_id=61 func=vf_ip_route_input_common line=2621 msg="find a route: flag=04000000 gw-10.5.20.70 via AZ" 4) Traffic will be matchd by policy ID 2. Id=20085 trace_id=61 func=init_ip_session_common line=5894 msg="allocate a new session-000d2315" 2) After that DNAT will happen: LOGIC: Step by step traffic flow for TASK 1 solution.ġ) When user A: 10.200.10.86 behind fortiGATE firewall ping dummy IP: 10.10.10.1 instead of pinging actual remote IP from phase 2 selector subnet: 10.210.10.84 traffic first hit port 3 ( FortiGate firewall LAN interface) and allocate a new session. # diagnose debug flow show function-name enable # diagnose debug flow filter saddr 10.200.10.86 Run flow filter logs to check if traffic is going out from policy in-out or not (here policy id is 2 and wan interface for FortiGate firewall is port 1).
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