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luca1994
luca1994
Explorer III
October 24, 2023
Solved

Policy doubt

  • October 24, 2023
  • 10 replies
  • 3819 views

Hello team,

 

i have a question abount policy match.

I have sniffed packets from fortigate CLI and the result is:

 

6.891062 port3 in 195.xx.xxx.xx -> 172.xx.xx.xxx: icmp: echo request
7.892226 port3 in 195.xx.xxx.xx -> 172.xx.xx.xxx: icmp: echo request
8.892875 port3 in 195.xx.xxx.xx -> 172.xx.xx.xxx: icmp: echo request

 

So I created a firewall policy having as source port3 and source ip address 195.xx.xxx.xx and as destination 172.xx.xx.xxx with service ICMP_ALL. But the policy not match.

 

Any suggestion?

 

Thanks for the support

 

 

Best answer by Toshi_Esumi

For a policy route to work, there need to be a proper route existing toward the same outgoing interface in the routing table.

For examiple, if two 0/0 routes to wan1 and wan2 exist, you can set two policy routes for one group of IPs to use wan1 for like 8.8.8.8/8.8.4.4 and another group of IPs to use wan2 for the same DNS servers.

But if there is only one 0/0 route to wan1, and no route toward wan2, the second group won't be able to reach the DNS servers. It wouldn't be able to use wan1 either because the policy route "sticks" and won't let it follow the 0/0 route.

 

Toshi

10 replies

dbu
Staff
dbu
Staff
October 24, 2023

Hello @luca1994 ,
What are you trying to achieve here ? 
This policy you mention is to allow all ICMP traffic.  

From sniffer output i see only echo requests. Are you failing to ping ?

Here is a guide how to troubleshoot connectivity issues:

Troubleshooting Tip: First steps to troubleshoot c... - Fortinet Community

    luca1994
    luca1994Author
    Explorer III
    October 25, 2023

    Hello @dbu , yes the ping failed. I would like the ping to pass.

     

    Thanks

    sw2090
    SuperUser
    sw2090
    SuperUser
    October 25, 2023

    the sniffer might not be the best way to debug that as it just shows the packets matching it but nothing more.

    In this case maybe some flow debug would provide more information.

     

    e.g.:

    diag debug enable

    diag debug flow filter clear

    diag debug flow filter saddr 195.81.187.35

    diag debug flow filter daddr 172.16.53.130

    diag debug flow trace start 1000

     

    then execute the ping from 195.81.187.35 to 172.16.53.130 and watch the output. It will show you which policy it matches and more details.

      luca1994
      luca1994Author
      Explorer III
      October 25, 2023

      Hello @sw2090 ,

       

      I performed what you described and the result is "reverse path check fail, drop"

       

      id=65308 trace_id=1 func=print_pkt_detail line=5842 msg="vd-root:0 received a packet(proto=1, 195.81.187.35:28234->172.16.53.130:2048) tun_id=0.0.0.0 from port3. type=8, code=0, id=28234, seq=1."
      id=65308 trace_id=1 func=init_ip_session_common line=6028 msg="allocate a new session-00cd0ce9, tun_id=0.0.0.0"
      id=65308 trace_id=1 func=ip_route_input_slow line=1723 msg="reverse path check fail, drop"
      id=65308 trace_id=1 func=ip_session_handle_no_dst line=6114 msg="trace"

       

      So I think there is a problem with the routing

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