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What are the chains in iptables filter table?
Iptables’s filter table has the following built-in chains. INPUT chain – Incoming to firewall. For packets coming to the local server. OUTPUT chain – Outgoing from firewall. For packets generated locally and going out of the local server. FORWARD chain – Packet for another NIC on the local server.
How to send packets with PREROUTING in iptables?
Inserting DOCKER -named filter INPUT/FORWARD rules fails because when Docker is restarted they are deleted then inserted (not appended). My best attempt is to insert another PREROUTING chain before Docker’s and send unwanted packets from eth0 (WAN) to a black hole – 0.0.0.1 – because you cannot DROP/REJECT in a nat table anymore.
What is the forward chain in iptables firewall?
The OUTPUT chain is for any packet leaving the system. And the FORWARD chain is for packets that are forwarded (routed) through the system. The screenshot below shows how to list the filter table and all its rules.
What’s the difference between PREROUTING and filter table?
The filter table is mainly used for filtering packets. We can match packets and filter them in whatever way we want. This is the place that we actually take action against packets and look at what they contain and DROP or /ACCEPT them, depending on their content.
How to add Netfilter raw table to kernel?
The raw table can be added to the kernel via make menuconfig Kernel modules → Netfilter Extensions → kmod-ipt-raw . This will enable the netfilter IP _NF_RAW config:
What are the Netfilter tables used in OpenWrt?
By default, OpenWrt uses three netfilter tables: filter, nat, mangle. These are sufficient to provide the desired netfilter functionality. Two other netfilter tables are: raw, security. The raw table can be added to the kernel via make menuconfig Kernel modules → Netfilter Extensions → kmod-ipt-raw.
What does a NAT table in Netfilter do?
Iptable’s NAT table has the following built-in chains. PREROUTING chain – Alters packets before routing. i.e Packet translation happens immediately after the packet comes to the system (and before routing). This helps to translate the destination ip address of the packets to something that matches the routing on the local server.