> Source: [sk162408](https://support.checkpoint.com/results/sk/sk162408)

# sk162408 - SCTP association cannot be established due to packet loss

| Property | Value |
|----------|-------|
| Solution ID | sk162408 |
| Date Created | 2019-09-23 |
| Last Modified | 2020-07-02 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |
| OS | Gaia |

## Symptoms

- * SCTP association cannot be established since specific SCTP packets (in this case cookie_echo packets) do not pass through the Security Gateway.

* No drops are seen in Kernel debug (# fw ctl zdebug drop), or in SmartLog.

* The issue is resolved upon disabling SecureXL.

* Other SCTP connections pass through the same gateway without any issues.

* Tcpdump traffic capture on the ingress interface shows cookie packets that are coming in:

  ![](https://sc1.checkpoint.com/sc/SolutionsStatics/sk162408/incoming1909130219.PNG)

  These packets are not seen in tcpdump on the egress interface:

  ![](https://sc1.checkpoint.com/sc/SolutionsStatics/sk162408/outgoing1909130219.PNG)
* Running: `# fwaccel stats -d` is showing multiple sanity errors:

  ![](https://sc1.checkpoint.com/sc/SolutionsStatics/sk162408/errors1909130214.png)
* When running SecureXL debug (`sim dbg -m ip + err`), it can be seen that the packet is dropped due to a "sanity error":  

  `
  [DATE TIME];[kern];[tid_2];[SIM-200130190]simi_sctp_sanity_checks: invalid SCTP packet length;`

## Cause

The issue originates from the fact that SecureXL checks for padding, while firewall module does not. SCTP packet need to be padded for 4 byte length, and SecureXL compared raw packet length to a calculated SCTP packet length, which resulted in it being unequal and therefore failing sanity check.

## Solution

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