User manual

User’s Manual InterCon-PrintServer
65
7.3 Allocation of the IP Address
Generally, TCP/IP Hosts may be addressed at the user command level (for example ping, ftp, tftp)
either by their names or directly via the Internet address. On the Internet protocol level only the
Internet address is used, and on the lower Ethernet protocol level the hardware address is used.
Allocation of hostnames, Internet and hardware addresses are saved in the files shown below:
/etc/hosts
allocation of hostnames to Internet address
/etc/bootptab
allocation of Internet address to hardware addresses
/etc/rarpd.cf
allocation of Internet address to hardware addresses
/etc/ethers
allocation of hostname to hardware addresses
The
/etc/hosts
file can be found on each computer connected to the network. The other files only
exist if special network services are implemented.
While the allocation of a hostname to the Internet address is saved in the
/etc/hosts
file, the
information about the allocation of the ‘Internet to hardware address’ is stored in an internal system
table. This table is managed by the 'Address Resolution Protocol' (ARP). The ARP table may be listed
and edited by the user command
arp
.
When the print server is switched on for the first time, it sends a broadcast message asking for its
Internet address. The protocols DHCP, BOOTP and RARP are used alternately. Whether the broadcast
message is sent or not, and which protocols are used, depends on the parameter settings.
If one of these services is available in the network and if its configuration file has the requested data,
an answer is sent to the print server. The print server now permanently saves its Internet address
(meaning that the print server will know its Internet address the next time it is switched on). When a
UNIX Computer addresses the print server host via ftp, it examines its ARP table for the hardware
address of the print server. If this address is non-existent (or out of date) the UNIX computer sends a
broadcast request for the address into the network using the ARP protocol. Since the print server
already knows the allocation, it answers the request. After updating the entry in its ARP table, the
UNIX computer tries to establish the
ftp
connection to the print server.
If neither a DHCP / BOOTP nor a RARP server responds to the print server’s Internet address request,
the print server host uses the first network telegram addressed to its hardware address to determine its
Internet address. In order to specifically send such a telegram, the UNIX computer must have the print
server’s hardware address listed its ARP table. This address must be manually entered into the ARP
table.
The TCP/IP print server host installation consists of the following steps. Depending on the UNIX
system used some of the following steps may be skipped:
•
Updating the
/etc/hosts
file
•
Updating the internal system ARP table.
(Skip if the DHCP/BOOTP or RARP service is implemented in your system)
or
•
Installation of a boot protocol
✘ ✘
The installation of the print server host must be done as a privileged user. The computer
used for this installation must be located in the same (sub-) network as the print server.