In network tracing of SMB problems, TCP reset abort occurs during validation negotiation. This article describes how to troubleshoot this situation.

TCP connection reset is a common problem when dealing with network communications based on the Server Message Block (SMB) protocol. This phenomenon may cause file transfer interruption, service unavailability, and even affect the stability of the entire network. This document describes how to troubleshoot TCP connection resets in the SMB protocol, helping you quickly restore the normal running of network services.

The SMB protocol is widely used in file sharing and printing services and relies on TCP/IP as the transport layer protocol. When a TCP connection is reset during SMB authentication negotiations, it usually means that communication between the client and server has been unexpectedly interrupted. This outage can be caused by a variety of reasons, including network configuration issues, firewall restrictions, incompatible protocol versions, or insufficient server resources.

Check network connection

Ping test: Run the ping command to check the basic network connectivity between the client and the server.

ping c 4 < Server IP address >

Traceroute: Run the traceroute command to check whether network paths are faulty.

traceroute < Server IP address >

Check firewall Settings. Ensure that the server's firewall allows traffic on SMB ports (TCP 445).

sudo ufw allow 445/tcp

Check the client firewall Settings to ensure that access to port 445 of the target server is allowed.

On the server side: Ensure that the SMB service is running.

sudo systemctl status smbd

Client: Try to connect to the server using the smbclient tool and check whether the connection is successful.

smbclient //< Server IP address >/share U username

Server-side logs: Check the log files of the Samba server, usually located in the /var/log/samba/ directory.

cat /var/log/samba/log.smbd

Client logs: On the client, check the logs related to the network connection, such as /var/log/syslog.

Server-side configuration: Check the configuration file of the Samba server (/etc/samba/smb.conf) to ensure that the protocol version is compatible with the client.

ini

[global]

smb protocol = SMB2,SMB3

Client configuration: Ensure that the SMB protocol versions supported by the client and server are the same.

Wireshark: Use the Wireshark tool to capture network traffic and analyze the reset causes of TCP connections.

sudo wireshark

In the Wireshark, filter tcp.port == 445 and check whether the RST flag exists.

Allow SMB traffic: Ensure that the server and client firewalls allow traffic on TCP 445 ports.

sudo ufw allow 445/tcp

sudo ufw reload

Update Samba versions: Make sure the Samba software on the server and client is up to date.

sudo apt update

sudo apt install samba

Adjust the SMB configuration file: Adjust parameters in the /etc/samba/smb.conf file, such as the protocol version and encryption Settings, as required.

Router/Switch: Check the configuration of network devices to ensure that there are no rules restricting SMB traffic.

VLAN Configuration: If VLAN is used, ensure that the client and server are in the correct VLAN.

System update: Periodically update the operating systems and Samba software of the server and clients.

sudo apt update

sudo apt upgrade

Network monitoring tools: Use network monitoring tools (such as Nagios and Zabbix) to continuously monitor network traffic and device status and identify potential problems in time.

Configuration backup: Periodically back up Samba configuration files and related Settings for easy troubleshooting and recovery.

SMB TCP reset problems can be caused by a variety of reasons, including network configuration, firewall restrictions, and protocol version incompatibility. By going through network connections, firewall Settings, log files, and protocol configurations step by step, problems can often be quickly located and resolved. In addition, regularly updating the system and monitoring the network status can effectively prevent the occurrence of such problems. If the problem persists, contact the network administrator or technical support team for further assistance.