H3C S3610-28P Operation Manual page 1011

Operation Manual – DHCP
H3C S3610&S5510 Series Ethernet Switches
Note:
The dhcp relay address-check enable command is independent of other
commands of the DHCP relay agent. That is, the invalid address check takes effect
when this command is executed, regardless of whether other commands are used.
You are recommended to configure IP address check on the interface enabled with
the DHCP relay agent; otherwise, the valid DHCP clients may not be capable of
accessing networks.
II. Configuring dynamic binding update interval
Via the DHCP relay agent, a DHCP client sends a DHCP-RELEASE unicast message
to the DHCP server to relinquish its IP address. In this case the DHCP relay agent
simply conveys the message to the DHCP server, thus it does not remove the IP
address from its bindings. To solve this, the DHCP relay agent can update dynamic
bindings at a specified interval.
The DHCP relay agent uses the IP address of a client and the MAC address of the
DHCP relay interface to regularly send a DHCP-REQUEST message to the DHCP
server.
If the server returns a DHCP-ACK message or does not return any message within
a specified interval, which means the IP address is assignable now, the DHCP
relay agent will update its bindings by aging out the binding entry of the IP
address.
If the server returns a DHCP-NAK message, which means the IP address is still in
use, the relay agent will not age it out.
Follow these steps to configure dynamic binding update interval:
Enter system view
Configure binding
update interval
III. Enabling unauthorized DHCP servers detection
There are unauthorized DHCP servers on networks, which reply DHCP clients with
wrong IP addresses.
With this feature enabled, upon receiving a DHCP message with the siaddr field (IP
address of the server assigning IP addresses to clients) not being 0 from a client, the
To do... Use the command...
system-view
dhcp relay security
tracker { interval | auto }
Chapter 3 DHCP Relay Agent Configuration
—
Optional
auto by default. (auto interval
is calculated by the relay
agent according to the
number of bindings.)
3-7
Remarks