Siemens S223, S323 user manual Dhcp Filtering, Dhcp Packet Filtering, Dhcp Server Packet Filtering

User Manual	UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

8.8.9DHCP Filtering

8.8.9.1DHCP Packet Filtering

For the hiD 6615 S223/S323, it is possible to block the specific client with MAC address. If the blocked MAC address by administrator requests IP address, the server does not assign IP. This function is to strength the security of DHCP server.

The following is the function of blocking to assign IP address on a port.

Command	Mode	Description
ip dhcp filter-port PORTS	Global	Configures a port in order not to assign IP.
no ip dhcp filter-port PORTS		Disables DHCP packet filtering.

The following is to designate MAC address which IP address is not assigned.

Command		Mode	Description
ip dhcp filter-address	MAC-		Blocks a MAC address in case of requesting IP ad-
			dress.
ADDR
		Global	MAC-ADDR: MAC address
no ip dhcp filter-address			Disables DHCP MAC filtering.
MAC-ADDR

8.8.9.2DHCP 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. 8.34, 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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