Dhcp Settings - ZyXEL Communications NXC2500 User Manual

If you set the bandwidth restrictions very high, you effectively remove the restrictions.
The NXC also restricts the size of each data packet. The maximum number of bytes in each packet
is called the maximum transmission unit (MTU). If a packet is larger than the MTU, the NXC divides
it into smaller fragments. Each fragment is sent separately, and the original packet is re-assembled
later. The smaller the MTU, the more fragments sent, and the more work required to re-assemble
packets correctly. On the other hand, some communication channels, such as Ethernet over ATM,
might not be able to handle large data packets.

DHCP Settings

Dynamic Host Configuration Protocol (DHCP, RFC 2131, RFC 2132) provides a way to automatically
set up and maintain IP addresses, subnet masks, gateways, and some network information (such
as the IP addresses of DNS servers) on computers in the network. This reduces the amount of
manual configuration you have to do and usually uses available IP addresses more efficiently.
In DHCP, every network has at least one DHCP server. When a computer (a DHCP client) joins the
network, it submits a DHCP request. The DHCP servers get the request; assign an IP address; and
provide the IP address, subnet mask, gateway, and available network information to the DHCP
client. When the DHCP client leaves the network, the DHCP servers can assign its IP address to
another DHCP client.
In the NXC, some interfaces can provide DHCP services to the network. In this case, the interface
can be a DHCP relay or a DHCP server.
As a DHCP relay, the interface routes DHCP requests to DHCP servers on different networks. You
can specify more than one DHCP server. If you do, the interface routes DHCP requests to all of
them. It is possible for an interface to be a DHCP relay and a DHCP client simultaneously.
As a DHCP server, the interface provides the following information to DHCP clients.
• IP address - If the DHCP client's MAC address is in the NXC's static DHCP table, the interface
assigns the corresponding IP address. If not, the interface assigns IP addresses from a pool,
defined by the starting address of the pool and the pool size.
Table 66 Example: Assigning IP Addresses from a Pool
START IP ADDRESS
50.50.50.33
75.75.75.1
99.99.1.1
120.120.120.100
The NXC cannot assign the first address (network address) or the last address (broadcast
address) in the subnet defined by the interface's IP address and subnet mask. For example, in
the first entry, if the subnet mask is 255.255.255.0, the NXC cannot assign 50.50.50.0 or
50.50.50.255. If the subnet mask is 255.255.0.0, the NXC cannot assign 50.50.0.0 or
50.50.255.255. Otherwise, it can assign every IP address in the range, except the interface's IP
address.
If you do not specify the starting address or the pool size, the interface the maximum range of IP
addresses allowed by the interface's IP address and subnet mask. For example, if the interface's
IP address is 9.9.9.1 and subnet mask is 255.255.255.0, the starting IP address in the pool is
9.9.9.2, and the pool size is 253.
1. At the time of writing, the NXC does not support ingress bandwidth management.
Chapter 8 Interfaces
POOL SIZE RANGE OF ASSIGNED IP ADDRESS
5 50.50.50.33 - 50.50.50.37
200 75.75.75.1 - 75.75.75.200
1023 99.99.1.1 - 99.99.4.255
100 120.120.120.100 - 120.120.120.199
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