Most Linux distributions will default to running a host-based firewall, iptables. If you want your hosts to communicate with each other, you have two options: turn off iptables or configure iptables to allow the communication. I prefer to leave iptables turned on and configure access. Keeping iptables is just another layer of your defence across the network.
Iptables, more properly referred to as "iptables/netfilter" because of the two modules that are involved -- the userspace module "iptables" and the kernel module "netfilter" -- is the firewall How to Install Iptables on CentOS 7 | Linuxize Feb 15, 2019 How to make iptables rules persistent after reboot on Dec 27, 2016
Feb 15, 2019
Config servers host the config database that stores metadata for sharded clusters. Config servers listen for connections on port 27019. As a result, add the following iptables rules to the config server to allow incoming and outgoing connection on port 27019, for connection to the other config servers. netfilter/iptables project homepage - The netfilter.org iptables is a generic table structure for the definition of rulesets. Each rule within an IP table consists of a number of classifiers (iptables matches) and one connected action (iptables target). netfilter, ip_tables, connection tracking (ip_conntrack, nf_conntrack) and the NAT subsystem together build the major parts of the framework. Configuring Felix - Project Calico
How to Set Up Gateway Using iptables and route on Linux
The iptables-persistent looks for the files rules.v4 and rules.v6 under /etc/iptables. These are just a few simple commands you can use with iptables, which is capable of much more. Read on to check on some of the other options available for more advanced control over iptable rules. Use iptables with CentOS 7 - Rackspace Support Install and configure iptables. Use the following steps to install and configure iptables: Install the iptables-services package (if it is not already installed) by running the following command: $ yum install iptables-services Enable the service to start at boot time by running the following commands: How To List and Delete Iptables Firewall Rules | DigitalOcean Aug 14, 2015 Easy IPTables Configuration and Examples on Ubuntu 16.04 Jan 29, 2018