IPSec tunnel not working

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IPSec tunnel not working

L1 Bithead


I have IPSec tunnel between Palo alto 820 and Cyberoam firewall. But It's not getting up. Neither Phase 1 nor Phase 2. Even I am not reachable to other end public ip. Suggest me. 


Cyber Elite
Cyber Elite

Initiate vpn from Cyberoam side towards Palo.

Do you see any sessions from Cyberoam public IP in "Monitor > Traffic" or "Monitor > Session Browser" on Palo side?

If yes check "Monitor > System" and use filter below. Do you see any errors that might reveal why tunnel don't come up?

( subtype eq vpn )


Enterprise Architect, Security @ Cloud Carib Ltd
Palo Alto Networks certified from 2011

Found this error in System log -   IKE phase-1 negotiation is failed as initiator, main mode.

Cyber Elite
Cyber Elite

This error is not helpful as if Palo is "initiator" then you need to check logs at Cyberoam side.

Only recipient side will know why connection failed. Recipient will not share failure reason with initiator.

If you want to analyze logs from Palo side you need to initiate connection from Cyberoam towards Palo..

Enterprise Architect, Security @ Cloud Carib Ltd
Palo Alto Networks certified from 2011


Error from Cyberoam firewall

I think @Raido_Rattameister suggested to you to switch the responder to be Palo Alto.


How to make Palo Alto Networks firewalls Responder-only in an IPSec tunnel





You will have to do some investigations or debugs like after making Palo Alto responder if the error is not clear to enable IKE debug or check for global counter drops or packet captures if the traffic is even reaching the Palo Alto firewall at all or if a security policy on Palo Alto is dropping it:










Cyber Elite
Cyber Elite

Does Cyberoam have 1 or more WAN IPs?


According to https://docs.sophos.com/nsg/sophos-firewall/17.5/Help/en-us/webhelp/onlinehelp/nsg/sfos/concepts/Log... error message 17842 shows success (<connectionname>, EST-P1-MM: Response to establishment request from <peeris> peer <peerrequesterip> successful) and error 17856 seems to mean that Cyberoam replied but did not get any answer after that (<connectionname>, EST-P1: max number of retransmissions <count> reached STATE_MAIN_I1. No response (or no acceptable response) to first IKE message.).


So first suspicion is that Palo sends IKE packet to Cyberoam WAN IP1 and Cyberoam replies to Palo from WAN IP2.

If this is the case then you need static route in Cyberoam to send return packets from WAN IP1 to Palo.


If Cyberoam  don't have 2 IPs then check that Palo firewall policy permits incoming IPSec traffic from Cyberoam IP and would not drop those packets.

Enterprise Architect, Security @ Cloud Carib Ltd
Palo Alto Networks certified from 2011

L1 Bithead

On Monitor > Traffic, check if you have any deny traffic from/to public IP address of the remote site.
When it's about phase 1 of IPsec, most of the time is about IKE parameters or the traffic is may be denied somewhere

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