To open the TFTP port in IPTables, we will run the rule:
sudo iptables -A INPUT -p udp --dport 69 -j ACCEPT
To open the TFTP port for a specific network only, we will run the rule:
sudo iptables -A INPUT -p udp -s 192.168.1.0/24 --dport 69 -j ACCEPT
To remove a rule, we’ll use the same command, replacing -A with -D, for example:
sudo iptables -D INPUT -p udp -s 192.168.1.0/24 --dport 69 -j ACCEPT
To view the list of rules, use the command:
sudo iptables -nvL
See also my articles:
Configuring IPTables
Installing and Configuring a TFTP Server in Ubuntu
Install and configure tftpd-hpa