3Com 8807 Configuration Manual page 695

Configuring Parameters
for DHCP Server to Send
Ping Packets
Displaying and
Debugging the DHCP
Server
If you execute the gateway-list command multiple times, the newly configured IP
addresses overwrite the existing ones.
To avoid address conflict caused by reassigning an in-use IP address, before
assigning an IP address to a DHCP client, the DHCP server detects the network
using the ping instructions to ensure the IP address is not occupied. The DHCP
server determines whether an IP address is reachable by sending specified number
of ping packets. It waits for response packet for a specified period after sending
each of these packets. If the DHCP server receives no response after sending all
these packets, it considers the IP address is not used by other devices in this
network and assigns the IP address to this DHCP client. Otherwise, it does not
assign the IP address.
Perform the following configuration in system view.
Table 646 Configure parameters for DHCP server to send ping packets
Operation
Set the maximum number of ping packets the
DHCP is allowed to send
Revert to the default maximum number
Set the maximum duration for the DHCP
server to wait for response to a ping packet
Revert to the default maximum duration
By default, the DHCP server sends up to 2 ping packets to test an IP address and
waits for a response for up to 500 milliseconds before it sends another ping
packet.
Note that the DHCP server detects address conflict by ping packets, whereas a
DHCP client does this by ARP packets.
After the above configuration, you can execute the display command in any view
to display operating information about the DHCP server to verify your
configuration, and execute the debugging command to enable debugging for
the DHCP server
Execute the following command in any view.
Table 647 Display the configuration information about the DHCP server
Operation
Display the statistics about DHCP address
conflicts
Display information about lease-expired
addresses in DHCP address pool(s). The
lease-expired IP addresses in an address pool
are assigned to other DHCP clients as needed
if the address pool runs out of its available IP
addresses
Display the ranges of available (unassigned) IP
addresses in DHCP address pools
Configuring DHCP Server
Command
dhcp server ping packets number
undo dhcp server ping packets
dhcp server ping timeout milliseconds
undo dhcp server ping timeout
Command
display dhcp server conflict { all | ip
ip-address }
display dhcp server expired { ip ip-address |
pool [ pool-name ] | interface [
vlan-interface vlan-id ] | all }
display dhcp server free-ip
695