Cambium PTP 450 series, User Manual

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PTP 450 User Guide Data network planning
2-80
ptp-450 (July 2014)
DHCP
DHCP enables a device to be assigned a new IP address and TCP/IP parameters, including a default gateway,
whenever the device reboots. Thus DHCP reduces configuration time, conserves IP addresses, and allows modules
to be moved to a different network within the Cambium system.
In conjunction with the NAT features, each BHS provides

a DHCP server that assigns IP addresses to computers connected to the BHS by Ethernet protocol.

a DHCP client that receives an IP address for the BHS from a network DHCP server.
DMZ
In conjunction with the NAT features, a DMZ (demilitarized zone) allows the assignment of one IP address behind
the BHS for a device to logically exist outside the firewall and receive network traffic. The first three octets of this
IP address must be identical to the first three octets of the NAT private IP address.
Developing an IP addressing scheme
Network elements are accessed through IP Version 4 (IPv4) addressing.
A proper IP addressing method is critical to the operation and security of a network.
Each module requires an IP address on the network. This IP address is for only management purposes. For security,
you should either

assign an unroutable IP address.

assign a routable IP address only if a firewall is present to protect the module.
You assign IP addresses to computers and network components by either static or dynamic IP addressing. You will
also assign the appropriate subnet mask and network gateway to each module.
Address Resolution Protocol
As previously stated, the MAC address identifies a module in

communications between modules.

the data that modules store about each other.
The IP address is essential for data delivery through a router interface. Address Resolution Protocol (ARP)
correlates MAC addresses to IP addresses.
For communications to outside the network segment, ARP reads the network gateway address of the router and
translates it into the MAC address of the router. Then the communication is sent to MAC address (physical network
interface card) of the router.
For each router between the sending module and the destination, this sequence applies. The ARP correlation is
stored until the ARP cache times out.
Allocating subnets
The subnet mask is a 32-bit binary number that filters the IP address. Where a subnet mask contains a bit set to 1,
the corresponding bit in the IP address is part of the network address.