Cyclades AlterPath KVM 16, Manual

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4: KVM Web Configuration
AlterPath KVM Manual 4-47
Network > IP Filtering
I
f you already understand how IP filtering works, skip this section
and proceed to the procedure section, IP Filtering - To Add a Chain .
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IP filtering refers to the selective blocking of the passage of IP packets between
global and local networks. The filtering is based on rules that describe the
characteristics of the packet (
e.g ., the contents of the IP header, the input/output
interface, or the protocol).
This feature is used mainly in firewall applications to filter the packets that could
potentially crack the network system or generate unnecessary traffic in the network.
The IP Filtering form is structured in two levels:
• Chain
• Rule
Structure of IP Filtering
IP Filtering configuration is structured on two levels:
• The IP Filtering form which contains a list of chains.
• The chains which contain the rules that control filtering.
Chain
The filter table contains a number of built-in chains and may include user-defined
chains. The built-in chains are called according to the type of packet. User-defined
chains are called when a rule which is matched by the packet points to the chain. Each
table has a set of built-in chains classified as follows:
• INPUT - For packets coming into the box itself.
• FORWARD - For packets being routed through the box.
• OUTPUT - For locally-generated packets.
Rule
Each chain has a sequence of rules that address the following:
• How the packet should appear in order to match the rule.
Some information about the packet is checked according to the rule, for example,
the IP header, the input and output interfaces, the TCP flags and the protocol.
• What to do when the packet matches the rule.
The packet can be accepted, blocked, logged or jumped to a user-defined chain.