Description
This article describes how to show if the VIP is configured on FortiGate and is getting denied by a forward policy check.
Scope
FortiGate.
Solution
- First, make sure that the site it is DNATing is reachable on the port mentioned. To do this, perform a telnet or ping test to that server by using the following commands:
execute ping <server-ip>
execute telnet <server-ip> <port>
- Below is an example of a configured VIP, custom service and Policy:
VIP configuration:
config firewall vip
edit "Test"
set id 0
set comment ''
set type static-nat
set extip 1.1.1.1
set nat44 enable
set nat46 disable
set mappedip "192.168.1.101"
set extintf "wan1"
set arp-reply enable
set nat-source-vip disable
set portforward enable
set gratuitous-arp-interval 0
set ssl-client-rekey-count 0
set color 0
set protocol tcp
set extport 4443
set mappedport 4443
set portmapping-type 1-to-1
next
end
Policy configuration:
config firewall policy
edit 2
set name "Virtual-IP"
set srcintf "wan1"
set dstintf "internal"
set action accept
set srcaddr "all"
set dstaddr "Test-VIP"
set schedule "always"
set service "test-vip-service"
set ssl-ssh-profile "certificate-inspection"
set nat disable
next
end
Custom service configuration:
config firewall service custom
edit "test-vip-service"
set uuid 4be63b06-5014-51ef-a95c-da8fe424ff05
set category "Web Access"
set tcp-portrange 4443:4443
next
end
- The debug output will show the following:
2024-08-01 09:11:56 id=65308 trace_id=3 func=get_new_addr line=1228 msg="find DNAT: IP-
192.168.1.101, port-4443"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_check_one_dnat_policy line=5223 m
sg="matched policy-1, act=accept, vip=1, flag=100, sflag=2000000"
2024-08-01 09:11:56 id=65308 trace_id=3 func=iprope_dnat_check line=5280 msg="result: s
kb_flags-02000000, vid-1, ret-matched, act-accept, flag-00000100"
2024-08-01 09:11:56 id=65308 trace_id=3 func=fw_pre_route_handler line=176 msg="VIP-192
.168.1.101:4443, outdev-wan1"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__ip_session_run_tuple line=3498 msg="DNAT
1.1.1.1:4443->192.168.1.101:4443"
2024-08-01 09:11:56 id=65308 trace_id=3 func=vf_ip_route_input_common line=2605 msg="fi
nd a route: flag=00000000 gw-192.168.1.101 via internal"
2024-08-01 09:11:56 id=65308 trace_id=3 func=iprope_fwd_check line=789 msg="in-[wan1],
out-[internal], skb_flags-020000c0, vid-1, app_id: 0, url_cat_id: 0"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_tree_check line=535 msg="gnum-100
004, use addr/intf hash, len=3"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_check_one_policy line=2047 msg="c
hecked gnum-100004 policy-3, ret-no-match, act-accept"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_check_one_policy line=2047 msg="c
hecked gnum-100004 policy-9, ret-no-match, act-accept"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_check_one_policy line=2047 msg="c
hecked gnum-100004 policy-0, ret-matched, act-accept"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_user_identity_check line=1822 msg
="ret-matched"
2024-08-01 09:11:56 id=65308 trace_id=3 func=__iprope_check_one_policy line=2265 msg="p
olicy-0 is matched, act-drop"
2024-08-01 09:11:56 id=65308 trace_id=3 func=iprope_fwd_check line=826 msg="after iprop
e_captive_check(): is_captive-0, ret-matched, act-drop, idx-0"
2024-08-01 09:11:56 id=65308 trace_id=3 func=iprope_fwd_auth_check line=845 msg="after
iprope_captive_check(): is_captive-0, ret-matched, act-drop, idx-0"
2024-08-01 09:11:56 id=65308 trace_id=3 func=fw_forward_handler line=757 msg="Denied by
forward policy check (policy 0)"
- Make the following changes in the custom service:
config firewall service custom
edit test-vip-service
set tcp-portrange 4443 <- Instead of 4443:4443.
next
end
- Since the source-port is not known, it cannot be specified in the configuration. Instead, disable 'Specify source port' from the GUI in the services.
- Note that DNAT takes place before the policy lookup. If the VIP object applies port translation (changing the external port to a different mapped port), ensure that the firewall policy for the VIP includes the destination port in the Services field. Otherwise, the traffic will not match it and will be dropped by the Implicit Deny policy.
Related article:
Troubleshooting Tip: VIP configured for filtering a specific source interface is getting 'Denied by ...
