ZyXEL Communications B-2000 用户手册
ZyAIR B-2000 Wireless LAN Gateway with 4-Port Switch
3-4
Internet Access
3.3.4 DHCP Configuration
DHCP (Dynamic Host Configuration Protocol) allows the individual clients (computers) to obtain the
TCP/IP configuration at start-up from a centralized DHCP server. The ZyAIR has built-in DHCP server
capability, enabled by default, which means it can assign IP addresses, an IP default gateway and DNS
servers to Windows 95, Windows NT and other systems that support the DHCP client. The ZyAIR can also
act as a surrogate DHCP server where it relays IP address assignment from the actual DHCP server to the
clients.
TCP/IP configuration at start-up from a centralized DHCP server. The ZyAIR has built-in DHCP server
capability, enabled by default, which means it can assign IP addresses, an IP default gateway and DNS
servers to Windows 95, Windows NT and other systems that support the DHCP client. The ZyAIR can also
act as a surrogate DHCP server where it relays IP address assignment from the actual DHCP server to the
clients.
IP Pool Setup
The ZyAIR is pre-configured with a pool of 32 IP addresses starting from 192.168.1.33 to 192.168.1.64 for
the client machines. This leaves 31 IP addresses, 192.168.1.3 to 192.168.1.32 (excluding the ZyAIR itself
which has a default IP of 192.168.1.1) for other server machines, for example, server for mail, FTP, telnet,
web, etc., that you may have.
the client machines. This leaves 31 IP addresses, 192.168.1.3 to 192.168.1.32 (excluding the ZyAIR itself
which has a default IP of 192.168.1.1) for other server machines, for example, server for mail, FTP, telnet,
web, etc., that you may have.
DNS Server Address
DNS (Domain Name System) is for mapping a domain name to its corresponding IP address and vice versa,
for example, the IP address of www.zyxel.com is 204.217.0.2. The DNS server is extremely important
because without it, you must know the IP address of a machine before you can access it. The DNS server
addresses that you enter in the DHCP setup are passed to the client machines along with the assigned IP
address and subnet mask.
for example, the IP address of www.zyxel.com is 204.217.0.2. The DNS server is extremely important
because without it, you must know the IP address of a machine before you can access it. The DNS server
addresses that you enter in the DHCP setup are passed to the client machines along with the assigned IP
address and subnet mask.
There are two ways that an ISP disseminates the DNS server addresses. The first is for an ISP to tell a
customer the DNS server addresses, usually in the form of an information sheet, when s/he signs up. If your
ISP does give you the DNS server addresses, enter them in the DNS Server fields in DHCP Setup,
otherwise, leave them blank.
customer the DNS server addresses, usually in the form of an information sheet, when s/he signs up. If your
ISP does give you the DNS server addresses, enter them in the DNS Server fields in DHCP Setup,
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 ZyAIR 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 ZyAIR 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 ZyAIR tells the DHCP clients that it itself is the DNS server. When a computer sends a DNS
query to the ZyAIR, the ZyAIR forwards the query to the real DNS server learned through IPCP and relays
the response back to the computer.
0.0.0.0, the ZyAIR tells the DHCP clients that it itself is the DNS server. When a computer sends a DNS
query to the ZyAIR, the ZyAIR 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
ZyAIR can pass the DNS servers to the computers and the computers can query the DNS server directly
without the ZyAIR’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
ZyAIR can pass the DNS servers to the computers and the computers can query the DNS server directly
without the ZyAIR’s intervention.