User's Manual

3 Detailed Description
APCD-LM043-4.0 49
The gateway router can provide DHCP server functionality, or you can implement a dedicated
DHCP server, as shown in Figure 27.
Figure 27 DHCP Relay
3.6.2 Port Filtering
The CCU and EUM both support TCP and UDP port filtering. The IP protocol suite is made up
of many subcomponents consisting of ports and protocols. Up-to-date listings of TCP and
UDP ports can be obtained off the Web. Some of these ports are required for normal LMS4000
operation, but most are not. The system operator can configure the CCU and EUM to filter
packets on specific TCP or UDP ports to improve network performance, security, or privacy.
For example, to prevent end-users from having visibility of, and access to, other end-users
through Windows Network Neighborhood, filter the following ports at the CCU for both UDP
and TCP packets:
• Port 137 NETBIOS Name Service
• Port 138 NETBIOS Datagram Service
• Port 139 NETBIOS Session Service
• Port 1512 Microsoft’s Windows Internet Name Service
CAUTION: The EUM is delivered with port filtering enabled.
CAUTION: Do not enable filters to block Telnet (port 23), FTP
(ports 20 and 21), or SNMP (ports 161 and 162); otherwise, you
will not be able to manage your network.
CCU3000
(with DHCP Relay enabled)
Antenna
EUM3000
NMS Station
Switch
Internet
End-user Computer
(with DHCP enabled)
DHCP Server
DHCP
Request
DHCP
Response
(layer-2
messages)
DHCP
Request
(UDP)
DHCP
Response
(UDP)
Router