# Dynamic Routing Manager failback causes "TCP out of state: First packet isn't SYN" drops

## Product
Maestro HyperScale Firewall, Scalable Chassis

## Version
R81 (EOS), R81.10 (EOS), R81.20

## OS
Gaia

## Last Modified
2024-07-01

## Symptoms
- After dynamic routing manager failure and recovery, connections are dropped with a log message "TCP out of state: First packet isn't SYN"
- Firewall kernel debug shows these connections were declared as zombie connections:

```bash
# fw ctl zdebug -m cluster + unisync
fwha_iter_should_handle_conn: ERROR: no member will do iterator for this conn (zombie?).;
conn_entry_iterator_cb: Deleting zombie connection;
```

## Cause
This scenario is unique when two Security Gateway Modules (SGMs) are configured in the security group along with dynamic routing protocol and there are symmetric connections on the non-SMO Security Gateway Module.

In such scenario, a connection can be considered as a zombie connection and not synchronized on SGM-1 recovery phase.

When SGM-1 is ready to be active again, the 'ROUTED' pnote is set on the SGM-2 to force its state to "Down" and moves the dynamic routing manager (DR manager) task back to SGM-1.

As the connection was not synchronized, it results in the connection drop

```bash
dropped by fw_first_packet_state_checks Reason: First packet isn't SYN;
```

## Solution
This problem was fixed. The fix is included in:

- [Jumbo Hotfix Accumulator for R81.20](https://sc1.checkpoint.com/documents/Jumbo_HFA/R81.20/Default.htm) starting from Take 70
- [Jumbo Hotfix Accumulator for R81.10](https://sc1.checkpoint.com/documents/Jumbo_HFA/R81.10/Default.htm) starting from Take 141
- [Jumbo Hotfix Accumulator for R81](https://sc1.checkpoint.com/documents/Jumbo_HFA/R81/Default.htm) starting from Take 99

If you choose not to upgrade, Check Point can supply a **Hotfix**. [Contact Check Point Support](https://www.checkpoint.com/support-services/contact-support/) to get a Hotfix for this issue.

A Support Engineer will make sure the Hotfix is compatible with your environment before providing the Hotfix.

For faster resolution and verification, please collect [CPinfo files](http://supportcontent.checkpoint.com/solutions?id=sk92739) from the Security Management Server and Security Gateways involved in the case.

**Hotfix installation instructions:**

Refer to [sk168597 - How to install a Hotfix](https://support.checkpoint.com/results/sk/sk168597).

#### NOTE
This solution has been verified for the specific scenario, described by the combination of Product, Version and Symptoms. It may not work in other scenarios.

## Article Properties
**Access Level**: General  
**Status**: Approved by TAC  
**Date Created**: 2024-01-09  
**Last Modified**: 2024-07-01