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OrtizJorge97
New Contributor

AWS Fortigate VM DNAT is not working.

Hi guys, 

I am not able to pull off a DNAT to access from external internet access to my web service hosted in the server in  private subnet managed by fortigate.

 

I am new into this networking area, could you guys help me out ?

This is what I have been trying.

 

I am accessing with web browser like http://<FGT-Public-Ip>:3002 and also doing telnet <FGT-Public-Ip> 3002.... both time out.

 

Traffic is reaching my fortigate, verified with 

diagnose sniffer packet port1 'tcp and port 3002' results below:

-----------------------------------------------------------------------------------------------

XXXXXXXX # diagnose sniffer packet port1 'tcp and port 3002'
Using Original Sniffing Mode
interfaces=[port1]
filters=[tcp and port 3002]
3.351276 XXX.XXX.9.57.59128 -> 10.0.0.10.3002: syn 3472599031
3.351345 XXX.XXX.9.57.59128 -> 10.0.0.10.3002: syn 89282952

 

Redirects to interface port1 private ip address port 3002

-----------------------------------------------------------------------------------------------

Ran sniffer packet for port2 where it should be forwarded the traffic....

XXXXXXXX # diagnose sniffer packet port2 'tcp and port 3002'
Using Original Sniffing Mode
interfaces=[port2]
filters=[tcp and port 3002]

 

Nothing displays here after telnet or http request in browser.

-----------------------------------------------------------------------------------------------

This is my VIP configuration, external ip address is the public ip address (aws elastic ip) of fgt which i will be accessing and which is mapped to phyisical interface fgt port1 10.0.0.10... 10.0.1.27 is the private server in the private subnet.

 

Screenshot 2024-12-14 at 12.22.23 p.m..png

 

This below is my Firewall Policy allowing traffic from port1 to the VIP

Screenshot 2024-12-14 at 12.25.03 p.m..png

 

This below is the TCP/3002 Service... originally i had set up to ALL services, but still did not work.

Screenshot 2024-12-14 at 12.27.13 p.m..png

 

 

interfaces

port1 -> 10.0.0.10

port2 -> 10.0.1.10

 

Subnets

public subnet 10.0.0.0/24 (my fgt vm is placed here)

private subnet 10.0.1.0/24 

 

Resources

Server -> 10.0.1.27 (Placed in 10.0.1.0/24 subnet)

 

Static route 1:

Destination: 10.0.1.0/24

Gateway IP: 0.0.0.0 (managed by fgt)

Interface: port2

 

More context:

The service itself is literally a docker with nginx mapped 0.0.0.0:3002 -> ::80

 

Executed telnet from fortigate cli and works so, service is accessible from fortigate..
XXXXXXXXX # execute telnet 10.0.1.27 3002
Trying 10.0.1.27...
Connected to 10.0.1.27.

 

I have a SSL-VPN tunnel managed by fgt as 10.0.3.0/24

and successfully I am able to do telnet 10.0.1.27 3002 or even also curl or from the browser http://10.0.1.27:3002


 

 

 

2 REPLIES 2
AEK
SuperUser
SuperUser

Hi

Try use diag debug flow instead of diag sniffer. It should give why traffic is blocked.

AEK
AEK
DPadula

Adding to @AEK's reply, these are the commands that he suggested. 
Technical Tip: Debug flow tool

The option 'diagnose debug flow show function-name enable' will give you the reason as he mentioned.

 

Regards

DPadula

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