32
DarkStar User Guide
3: Software
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The second file is the DHCP server configuration file, which configures the server to provide the DHCP offer when it receives a
DHCP discovery request from the DarkStar system. It is essential that the information in the server configuration file match the
client identifier or source MAC address sent by the DarkStar system during DHCP discovery.
It is important to note that “01:” will always be prepended to an interface's MAC address when it is used as the DHCP client
identifier. The same syntax must be used in the DHCP server configuration file.
The information included in the DHCP server configuration file must correspond to the parameters (or absence of parameters)
in the boot host dhcp command stored in
startup-config
.
When the command
boot host
dhcp
interface_id
is present in the configuration file, Boot prepends
01:
to the MAC
address associated with the named interface; it uses the resulting string as the client identifier option in the discovery
messages sent on every active interface. This information may be useful in identifying a system by one unique address
regardless of which actual interface contacts the dhcp server. Note that the server's configuration file must include that string
in an option dhcp-client-identifier entry.
If Boot finds a
boot host dhcp
command in startup-config without a specified
<client-id interface>
, then Boot
broadcasts a DHCP discovery message on each active interface and in each instance the client identifier will be the MAC
address of the interface from which discovery is broadcast. In this scenario, you may use any active interface's client identifier
or source MAC address in the corresponding DHCP server configuration file. Be aware, however, that if the Ethernet interface
or MAC address that you designate in the file is unable to reach the DHCP server, no DHCP offer can be made and the configu-
ration process will fail.
The following example illustrates a portion of the required configuration of a Unix/dhcpd-based server. The following sample
would be added to the server's
/etc/dhcpd.conf
file:
host dxm-sea-01 {
hardware ethernet 00:A0:E3:00:01:A8;
next-server 10.3.0.250;
filename "config-00.01.a8";
}
00:A0:E3:00:01:A8
is the MAC address of an active Ethernet interface that can reach the DHCP server.
In all cases, the DarkStar system only temporarily uses the offered IP address and then releases it after obtaining the configu-
ration file.
Static IP configuration and other configuration parameters should be included in the file config-00.01.a8 that is placed in the
TFTP server's directory. The TFTP server is specified in the next-server parameter.
If the DarkStar system is multihomed and capable of reaching DHCP servers on more than one of its connected Ethernet ports,
you can specify a configuration file bound to a particular
dhcp-client-identifier
as illustrated in the following
example. In this case, a
boot host dhcp ethernet 0
line should be added to the
startup-config
of dxm-sea-01,
where the MAC address of Ethernet 0 on dxm-sea-01 is
00:A0:E3:00:01:A6
. This modification will allow the DHCP server
to provide a single configuration regardless of which DarkStar system management interface is used to obtain the configu-
ration:
host dxm-sea-01 {
next-server 10.3.0.32;
option dhcp-client-identifier 01:00:A0:E3:00:01:A6;
filename "config-00.01.a6";
}
