User guide

MDX-ETHERNET User Guide 17
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5.7 DHCP considerations
5.7.1 Using fixed IP addressing
Using fixed IP addresses (manually configured) on MDX-ETHERNET means that if a
module fails, the IP address can be restored to a replacement module without the need
to reconfigure the DHCP server. Using fixed addresses also prevents the DHCP server
from changing the address. When using fixed IP addresses, it is vital that the MDX-
ETHERNET IP address is reserved on the DHCP server to prevent duplicate
addressing.
5.7.2 Using DHCP
If DHCP is used it is recommended that the allocated IP address is allocated MDX-
ETHERNET's MAC address, this strategy prevents the IP address changing on the
MDX-ETHERNET.
Any leased addresses should be leased permanently to prevent IP address changes.
5.8 Basic principles of routing
Routing is required to get TCP/IP packets from one subnet to another. In an IP network
nodes from one subnet cannot communicate directly with nodes on a different subnet.
To allow nodes to communicate, a router (or similar device) is required to allow the two
subnets to exchange data. This means that any node wishing to communicate with a
node that is not on its own subnet, must know the address of a router that is on its own
subnet. This is sometimes called a gateway or default gateway.
If using manual IP address configuration please note that the IP address subnet mask
and the default gateway must also be set manually.
NOTE
If MDX-ETHERNET is configured to use DHCP and the module requires exchanging,
the new MDX-ETHERNET module will have a different MAC address and hence the
DHCP server will issue the new module with a different IP address.
NOTE