Ipsec VPN couldn't established.

Hello Dinesh Kandeeban ,

Kindly refer to the below KBA for IPsec not establishing troubleshooting steps:

support.sophos.com/.../KBA-000006520

HI Mayur,

        I have gone through the document already. I debugged the tunnel logs still unable to identify the issue 

Hi Dinesh,

Thank you for reaching out to Sophos Community.

Can you share any VPN error logs? 

You may check the following KBs for reference on troubleshooting and collecting logs.

•  Sophos Firewall: Troubleshooting site to site IPsec VPN issues 
• Check logs and configurations

Hi Erick,

       I have attached the tunnel logs snapshot. For the security purpose I have hidden the both location IP address 

Seems port 500 is closed from ISP router 

Hi Bharat,

         I don't think so, phase 2 for one subnet is flapping like up and down. If it is port 500 is blocked the tunnel for phase 2 for the specific subnet won't come up. 

Hi Bharat,

         I don't think so, phase 2 for one subnet is flapping like up and down. If it is port 500 is blocked the tunnel for phase 2 for the specific subnet won't come up. 

Hi  Dinesh Kandeeban

Please provide more information as below

IPSec Tunnel configured between Sophos Firewall to Sophos Firewall or third party firewall ?

Please share logs with option 4 as well with IPSec VPN Policy screenshots

and 

console>tcpdump 'port 500

Regards