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CLI
Management Guide
TigerAccess™ EE
336
SMC7824M/VSW
8.6.10 DHCP
Filtering
8.6.10.1
DHCP Packet Filtering
For the switch, it is possible to block the specific client with MAC address. If the MAC ad-
dress blocked by administrator requests an IP address, the server does not assign IP ad-
dress. This function can provide the security of DHCP server.
Not to assign IP address for specific client of a port, use the following command.
Command Mode
Description
ip dhcp filter-port
PORTS
Configures a port in order not to assign IP address.
no ip dhcp filter-port
PORTS
Global
Disables DHCP packet filtering.
Not to assign IP address for specific client with a specific MAC address, use the following
command.
Command Mode
Description
ip dhcp filter-address
MAC-
ADDR
Blocks a MAC address in case of requesting IP ad-
dress.
MAC-ADDR: client’s MAC address
no ip dhcp filter-address
MAC-ADDR
Global
Disables DHCP MAC filtering.
8.6.10.2
DHCP Server Packet Filtering
Dynamic Host Configuration Protocol (DHCP) makes DHCP server assign IP address to
DHCP clients automatically and manage the IP address. Most ISP operators provide the
service as such a way. At this time, if a DHCP client connects with the equipment that can
be the other DHCP server such as Internet access gateway router, communication failure
might be occurred.
DHCP filtering helps to operate DHCP service by blocking DHCP request which enters
through subscriber’s port and goes out into uplink port or the other subscriber’s port and
DHCP reply which enters to the subscriber’s port.
In the
Fig. 8.37
, server A has the IP area from 192.168.10.1 to 192.168.10.10. Suppose a
user connects with client 3 that can be DHCP server to A in order to share IP address
from 10.1.1.1 to 10.1.1.10.
Here, if client 1 and client 2 are not blocked from client 3 of DHCP server, client 1 and cli-
ent 2 will request and receive IP from client 3 so that communication blockage will be oc-
curred. Therefore, the filtering function should be configured between client 1 and client 3,
client 2 and client 3 in order to make client 1 and client 2 receive IP without difficulty from
DHCP server A.
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