iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT I know the last rule allows UDP to the lo interface. But, I thought all I needed was outgoing TCP for NEW/ESTABLISHED connections + incoming TCP for ESTABLISHED connections. It seemed counter-intuitive to me (because I'm still learning).

$ sudo iptables -I INPUT 1 -i lo -j ACCEPT. This command is very similar to the ones above:-I INPUT 1 - Insert a rule to the "input" chain in the 1st slot-i lo - Apply the rule to the loopback interface-j ACCEPT - Set it to accept traffic to the input chain when using tcp on port 443; How to Use Netfilter on Your Linux System: Enabling a The first iptables command, for example, appends to the INPUT chain (-A INPUT) the rule that if the packet doesn’t come from the lo interface (-i ! lo), iptables rejects the packet (-j REJECT). Before rejecting all other packets, you may add more rules to each INPUT chain to allow specific packets in. iptables: Linux firewall rules for a basic Web Server

# Allow loopback iptables -I INPUT 1 -i lo -j ACCEPT # Allow DNS iptables -A OUTPUT -p udp --dport 53 -j ACCEPT # Now, allow connection to website serverfault.com on port 80 iptables -A OUTPUT -p tcp -d serverfault.com --dport 80 -j ACCEPT iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT # Drop everything iptables -P INPUT

Aug 14, 2015 · Introduction. Iptables is a firewall that plays an essential role in network security for most Linux systems. While many iptables tutorials will teach you how to create firewall rules to secure your server, this one will focus on a different aspect of firewall management: listing and deleting rules. iptables is a pure packet filter when using the default 'filter' table, with optional extension modules. This should simplify much of the previous confusion over the combination of IP masquerading and packet filtering seen previously.

iptables -I INPUT --jump ACCEPT --in-interface lo iptables -I INPUT --jump ACCEPT --source localhost The first of these accepts all local traffic, on the lo interface, regardless of its IP address. The second one accepts all traffic from, regardless of what interface …

iptables is a user-space utility program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores. Different kernel modules and programs are currently used for different protocols; iptables applies to IPv4, ip6tables to IPv6, arptables to ARP, and ebtables to Ethernet frames. Linux iptables Command Examples and Guide [root@rhel01 root]# iptables -n -L -v --line-numbers Chain INPUT (policy DROP 7871 packets, 646K bytes) num pkts bytes target prot opt in out source destination 1 0 0 ACCEPT all -- lo * 2 2144 191K ACCEPT all -- * * state RELATED,ESTABLISHED 3 0 0 ACCEPT tcp -- * * tcp dpt:22 4 0 0 Use iptables with CentOS 7 - Rackspace $ yum install iptables-services Enable the service to start at boot time by running the following commands: $ systemctl enable iptables $ systemctl enable ip6tables Next, add iptables rules. You can do this in either of the following ways: From the command-line interface (CLI), by running commands similar to iptables -I INPUT