Aethra StarVoice, Руководство по установке, Страница: 23 / 39

The mechanism is based on the formulation of rules used to filter incoming and outgoing
traffic. The rules are contained in one or more lists, defined as Access Lists. Every Access
List is made up of a variable number of command lines (entries) that are given based on the
insertion order. The last entry, which is always present, although not visible, (in advanced
mode) is of “deny any” type: it only directs the contents of permit entries and rejects the
rest.
Every Access List can be assigned to one or more interfaces (LAN0, WAN1, …, WAN8).
Multiple Access Lists can be associated with each interface.
By assigning an Access List to the interface, every incoming packet from the interface is
checked based on the list rules.
Each rule contains a permission (“permit”) or negation (“deny”) clause. Three situations are
possible:
the packet meets the conditions of the rule and the rule is “deny” rule: the packet is
discarded immediately;
⇒
⇒
⇒
the packet meets the conditions of the rule and the rule is a “permit” rule: the packet
is sent to the routing function that routes the packet to the destination interface,
without additional checks;
the packet does not meet the conditions of the rule: the packet is subjected to the next
rule in the Access List.
If the packet does not meet any rule in the list, the packet is discarded.
4.6.7 Multicast traffic
StarVoice can process incoming multicast traffic to the interface (if enabled to multicast)
and replicate it over all interfaces enabled to multicast (except for the interface that
originates traffic).
4.6.8 DHCP and DNS services
These services are used to make LAN configuration easier and faster. If the DHCP service
is enabled, LAN hosts can be configured with the TCP/IP information supplied by
StarVoice (IP address and host name, IP address of DSN and WINS servers, default
gateway).
Hosts can use StarVoice as DNS server. StarVoice resolves local host names directly and,
when it cannot do it, sends requests to the external DNS server, tracing DNS records on
internal cache memory.
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