QTECH
Software Configuration Manual
11-149
·
yiaddr : IP address that the DHCP server assigns to a client.
·
siaddr : IP address of the DHCP server.
·
giaddr : IP address of the first DHCP relay agent that the DHCP client passes after it sent the request
packet.
·
chaddr : Hardware address of the DHCP client.
·
sname : Name of the DHCP server.
·
file : Name of the start configuration file that the DHCP server specifies for the DHCP client.
·
option : Optional variable-length fields, including packet type, valid lease time, IP address of a DNS
server, and IP address of the WINS server.
11.2.9.5
DHCP Packet Processing Modes
After the DHCP server is enabled on a device, the device processes the DHCP packet received from a DHCP
client in one of the following three modes depending on your configuration :
·
Global address pool : In response to the DHCP packets received from DHCP clients, the DHCP
server picks IP addresses from its global address pools and assigns them to the DHCP clients.
·
Interface address pool : In response to the DHCP packets received from DHCP clients, the DHCP
server picks IP addresses from the interface address pools and assigns them to the DHCP clients. If there
is no available IP address in the interface address pools, the DHCP server picks IP addresses from its
global address pool that contains the interface address pool segment and assigns them to the DHCP
clients.
·
Trunk : DHCP packets received from DHCP clients are forwarded to an external DHCP server,
which assigns IP addresses to the DHCP clients.
You can specify the mode to process DHCP packets. For the configuration of the first two modes, see DHCP
Server Configuration. For the configuration of the trunk mode, see DHCP Relay Agent Configuration.
One interface only corresponds to one mode. In this case, the new configuration overwrites the previous one.
11.2.9.6
Protocols and Standards
Protocol specifications related to DHCP include :
·
RFC2131 : Dynamic Host Configuration Protocol
·
RFC2132 : DHCP Options and BOOTP Vendor Extensions
·
RFC1542 : Clarifications and Extensions for the Bootstrap Protocol
11.3 DHCP server configuration list
DHCP packet is broadcasting packet so in layer 3 network structure and using DHCP to distribute IP address,
each broadcasting domain needs a DHCP server. For layer 3 network structure by using QTECH QSW-3900 to
establish a layer 3 network, each VLAN needs a DHCP server which greatly wastes of resources. A better way to
solve this problem is to configure DHCP relay in QTECH QSW-3900 to relay DHCP packet to DHCP server which
can need at least only one DHCP server.
Following DHCP functions are supported :
·
Support DHCP relay function
·
Support specifying DHCP server for each layer 3 interface
·
support built-in DHCP server
·
support at most 12 address pools and at most 8 network interfaces for each address pool
·
support DHCP client to obtain system IP
DHCP configuration list is as following :
·
Enable DHCP relay
·
Configure DHCP server
·
Specify DHCP server for layer 3 interface
·
Display DHCP server configuration
