Introduction for Administrative Users > Firewall/Packet Filtering on the OnBoard > Chains

Chains
A chain is a kind of named profile that includes one or more rules that define the following:
The OnBoard comes with a number of built-in chains with hidden rules that are preconfigured to control communications between devices that are connected to the OnBoard’s private Ethernet ports and devices on the public side of the OnBoard. The default chains are defined in “filter” and “nat” iptables. The “mangle” table is not used.
The built-in chains are named according to the type of packets they handle, as shown in the following lists. The first three chains listed below are in the iptables “filter” table.
The three chains listed below are in the “nat” table. These chains implement NAT (network address translation) including the redirecting packets addressed to a virtual IP to the device’s real IP address and hiding the device’s real IP address when the device sends packets to the authorized user:

Introduction for Administrative Users > Firewall/Packet Filtering on the OnBoard > Chains