ZXR10 8900 Series User Manual (Basic Configuration Volume)
DHCP Relay
Routers do not send the received broadcast packet from a sub-net-
work to another by default. But the router as the default gateway
of the client host must send the broadcast packet to the sub-net-
work where the DHCP server locates when the DHCP server and
client host are not in the same sub-network. This function is called
DHCP relay.
ZXR10 8900 series switch can act as a DHCP server or DHCP relay
to forward DHCP information.
DHCP Snooping Overview
DHCP brings convenience for IP address allocation, but it also
brings problems.
DHCP service allows multiple DHCP servers to exit in a subnet.
Therefore, the administrator cannot ensure that IP addresses of
users are allocated by the designated DHCP server. The addresses
may be allocated by DHCP servers that are set by other users
illegally.
In a DHCP service subnet, hosts with legal IP addresses and masks
can access this subnet. DHCP server may allocate these legal ad-
dresses to other hosts. This causes address confliction.
To solve the above problems, ZXR10 8900 series switch uses DHCP
snooping function to prevent bogus DHCP server in a subnet. The
port connecting with DHCP server must be set as trust port. Com-
bining with dynamic ARP inspection technology, DHCP snooping
function prevents binding of illegal IP and MAC. This ensures the
server to allocate IP addresses correctly.
Configuring DHCP
Configuring DHCP Server
To configure DHCP server, perform the following steps.
Step Command
Function
1
ZXR10(config)#
ip dhcp enable
This enables DHCP server
process globally.
2
ZXR10(config)#
ip local pool
<
pool-name
><
low-ip-add
ress
><
high-ip-address
><
net-mask
>
This configures an IP address
pool for a DHCP server.
3
ZXR10(config)#
ip dhcp server leasetime
<
time
>
This sets the lease time of the
IP address leased by a DHCP
server to client.
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