ZyXEL 791R 91-004-247001B Manual Do Utilizador
Códigos do produto
91-004-247001B
Prestige 791R G.SHDSL Router
6-4 LAN
your ISP does give you the DNS server addresses, enter them in the DNS Server fields in DHCP Setup,
otherwise, leave them blank.
otherwise, leave them blank.
Some ISP’s choose to pass the DNS servers using the DNS server extensions of PPP IPCP (IP Control
Protocol) after the connection is up. If your ISP did not give you explicit DNS servers, chances are the
DNS servers are conveyed through IPCP negotiation. The Prestige supports the IPCP DNS server
extensions through the DNS proxy feature.
Protocol) after the connection is up. If your ISP did not give you explicit DNS servers, chances are the
DNS servers are conveyed through IPCP negotiation. The Prestige supports the IPCP DNS server
extensions through the DNS proxy feature.
If the Primary and Secondary DNS Server fields in DHCP Setup are not specified, for instance, left as
0.0.0.0, the Prestige tells the DHCP clients that it itself is the DNS server. When a computer sends a DNS
query to the Prestige, the Prestige forwards the query to the real DNS server learned through IPCP and
relays the response back to the computer.
0.0.0.0, the Prestige tells the DHCP clients that it itself is the DNS server. When a computer sends a DNS
query to the Prestige, the Prestige forwards the query to the real DNS server learned through IPCP and
relays the response back to the computer.
Please note that DNS proxy works only when the ISP uses the IPCP DNS server extensions. It does not
mean you can leave the DNS servers out of the DHCP setup under all circumstances. If your ISP gives you
explicit DNS servers, make sure that you enter their IP addresses in the DHCP Setup menu. This way, the
Prestige can pass the DNS servers to the computers and the computers can query the DNS server directly
without the Prestige’s intervention.
mean you can leave the DNS servers out of the DHCP setup under all circumstances. If your ISP gives you
explicit DNS servers, make sure that you enter their IP addresses in the DHCP Setup menu. This way, the
Prestige can pass the DNS servers to the computers and the computers can query the DNS server directly
without the Prestige’s intervention.
6.1.6 IP Multicast
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender – 1 recipient) or
Broadcast (1 sender – everybody on the network). Multicast is a third way to deliver IP packets to a group
of hosts on the network - not everybody.
Broadcast (1 sender – everybody on the network). Multicast is a third way to deliver IP packets to a group
of hosts on the network - not everybody.
IGMP (Internet Group Multicast Protocol) is a network-layer protocol used to establish membership in a
multicast group - it is not used to carry user data. IGMP version 2 (RFC 2236) is an improvement over
version 1 (RFC 1112) but IGMP version 1 is still in wide use. If you would like to read more detailed
information about interoperability between IGMP version 2 and version 1, please see sections 4 and 5 of
RFC 2236. The class D IP address is used to identify host groups and can be in the range 224.0.0.0 to
239.255.255.255. The address 224.0.0.0 is not assigned to any group and is used by IP multicast computers.
The address 224.0.0.1 is used for query messages and is assigned to the permanent group of all IP hosts
(including gateways). All hosts must join the 224.0.0.1 group in order to participate in IGMP. The address
224.0.0.2 is assigned to the multicast routers group.
multicast group - it is not used to carry user data. IGMP version 2 (RFC 2236) is an improvement over
version 1 (RFC 1112) but IGMP version 1 is still in wide use. If you would like to read more detailed
information about interoperability between IGMP version 2 and version 1, please see sections 4 and 5 of
RFC 2236. The class D IP address is used to identify host groups and can be in the range 224.0.0.0 to
239.255.255.255. The address 224.0.0.0 is not assigned to any group and is used by IP multicast computers.
The address 224.0.0.1 is used for query messages and is assigned to the permanent group of all IP hosts
(including gateways). All hosts must join the 224.0.0.1 group in order to participate in IGMP. The address
224.0.0.2 is assigned to the multicast routers group.