"IPsec (ESP) packet dropped" Log found on Sonicwall Firewall

Hello All,

I found "IPsec (ESP) packet dropped" events in attempts section in Sonicwall GMS.
Can anyone help me to resolve this issue.

Yogiraj Pattani
Yogiraj PattaniInformation Security AnalystAsked:
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Blue Street TechLast KnightCommented:
Hi Yogiraj,

What kind of tunnel is it? Do you have Keep Alive on?

Run a Packet Capture and post the drop codes.

Let me know!
Yogiraj PattaniInformation Security AnalystAuthor Commented:
Yes keep alive is on and drop code is 21
Blue Street TechLast KnightCommented:
What SonicOS version are you running?
Yogiraj PattaniInformation Security AnalystAuthor Commented:
SonicOS Version :
Firewall Model : NSA 3600
Blue Street TechLast KnightCommented:
Thanks...not sure how I missed your post and not sure why mine showed twice but I cleaned them up nonetheless.

Anyway, in SonicOS 6.2+ the Drop-Code & Module-ID are provided in the description within the packet capture utility.

Drop-Code 21 means that packets are dropping on egress due to an invalid interface. This points to tunnel config. What is the Module-ID field in the Packet Capture (it should be after the Drop-Code field)? Is it 20? Re-configure the interfaces on both ends, make sure you can ping the other side, and that the IP addresses are up and responding. Then check the config of the tunnel and make sure the IP Address info is correct and the tunnel config is matching on both sides.

Dial in your MTU on both side for greater efficiency and faster throughput. Here's a guide on how to do this: https://www.experts-exchange.com/articles/12615/Unstable-Slow-Performing-Networks-or-VPNs-just-go-grocery-shopping.html

Can you tell me more about your tunnel.
  • Has the tunnel ever been up or is this an intermittent issue?
  • What Key Exchange are you using on each side: Aggressive Mode, Main Mode or IKEv2 Mode?
  • Do both sites have static Public IP address?

Let me know!

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