SENA Rhio10 - Manual (Page 20)

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with the help of the subnet mask. If the address is proven to be on the same network segment
as the Rhio10, the connection is established directly from the Rhio10. Otherwise, the
connection is established through the given default gateway.
A gateway is a network point that acts as an entrance to another network. Usually, the
computers that control traffic within the network or at the local Internet service provider are
gateway nodes. The Rhio10 needs to know the IP address of the default gateway computer in
order to communicate with the hosts outside the local network environment. For correct
information on the gateway IP address, please refer to the network administrator.
3.1.2 DHCP
Dynamic Host Configuration Protocol (DHCP) is a communications protocol that lets network
administrators manage and automate the assignment of IP addresses centrally in an
organization's network. DHCP lets a network administrator supervise and distribute IP
addresses from a central point and automatically send a new IP address when a computer is
plugged into a different place in the network.
As described in the section 3.1, the IP address must be entered manually at each computer in
Static IP mode and, if computers move to another location in another part of the network, a new
IP address must be entered. Meanwhile, all the parameters including the IP address, subnet
mask, gateway, DNS servers will be automatically configured when the IP address is assigned
in DHCP mode. DHCP uses the concept of a "lease" or amount of time for which a given IP
address will be valid for a computer. All the parameters required to assign an IP address are
configured on DHCP server side, and each DHCP client computer receives this information
when the IP address is provided at its boot-up.
To obtain an IP address, the Rhio10 sends a corresponding DHCP request as a broadcast over
the network after each reset. The reply generated by the DHCP server contains the IP address
as well as the subnet mask, gateway address, DNS servers and the lease time. The Rhio10
immediately places this information in its non-volatile memory. If the operating time reaches the
lease time, the Rhio10 will request the DHCP server for renewal of its lease time. If the DHCP
server approves extending the lease, the Rhio10 can continue to work with the current IP
address. Otherwise, the Rhio10 will start the procedure to request a new IP address to the
DHCP server.
A DHCP sever assigns IP addresses dynamically from an IP address pool, which is managed
by the network administrator. This means DHCP client, i.e. the Rhio10, receives a different IP
address each time it boots up. To prevent the case that users do not know the IP address of the