ZyXEL Communications USG110, Руководство пользователя

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Chapter 10 Interfaces
ZyWALL USG Series User’s Guide
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• Egress bandwidth sets the amount of traffic the Zyxel Device sends out through the interface to the
network.
• Ingress bandwidth sets the amount of traffic the Zyxel Device allows in through the interface from the
network.At the time of writing, the Zyxel Device does not support ingress bandwidth management.
If you set the bandwidth restrictions very high, you effectively remove the restrictions.
The Zyxel Device 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 Zyxel
Device 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 Zyxel Device, 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.