In nPath configuration, BIG-IP does not send ICMP reply to the L3 switch.

Hi KaiTT , 

> you should change your configuration little bit , use one of two scenarios :

1.  Change the default gateway for "20.20.20.1" instead of using Bigip self-ip as a gateway , and configure
   ( SNAT automap or SNAT pool ). 
   by this scenario , ICMP traffic should go through L3 swith without forward it to Big-ip
   All of this with respect to your routes.
2. Configure a fast layer 4 virtual server on your Big-ip and do not assign tcp profile to it , allow all protocols. 
   After creating it , go to virtual address and configure "echo-reply = disabled " not "always" 
   like below : 
   

in this scenario , ICMP traffic should go through Bigip to server 20.20.20.10 and return back to F5 big-ip " its gateway" 

> you only need to adjust your traffic flow , I recommend to do the first scenatio , using SNAT is very useful , so try it. 

Regards. 

Hi Kai,

Because the server needs to verify the source IP.

I understand that if I change the G/W of the server to L3 and configure Automap, I need the X-forward-for function to check the source IP.

However, the G/W of the server was configured as L4 because the end customer was not able to use the X-forwared-for feature.

I searched on the forum and I think it can be solved with forwarding virtual server.

Is it possible to solve it with the configuration below?

ltm virtual Forwading_VS {

   creation-time 2021-08-20:21:22:48

   destination 0.0.0.0:any

   ip-forward

   ip-protocol tcp

   last-modified-time 2021-08-21:10:00:37

   mask 255.255.255.255

   profiles {

       fastL4 { }

   }

   serverssl-use-sni disabled

   source 0.0.0.0/0

   source-address-translation {

       type automap

   }

   translate-address disabled

   translate-port disabled

   vs-index 6