dhcpcemu(8)dhcpcemu(8)NAMEdhcpcemu - Emulate a DHCP client
SYNOPSIS
/usr/sbin/dhcpcemu [-b] [-q] [-m | -n | -v] [-dn] [-a server_address]
[-c client_address] [-e hardware_address] [-h hostname] [-i
client_identifier] [-r requested_address] [-p bootp | discover | renew
| rebind | request | select | decline] [-s size] [-t timeout] [-f file]
interface
OPTIONS
Sets the broadcast bit. Runs quietly: display neither the contents of
the incoming nor the outgoing packets. Sets the magic cookie in the
outgoing packet to be the CMU (-m) or the RFC1048 (-v ) value (the
default). The -n option means to use no cookie at all. The server
identifier field in the options of the outgoing packet is set to the IP
address. To properly emulate a client in the selecting DHCP state,
this field is required regardless of the value given with the -p
option. Sets the ciaddr field in the packet to the value
client_address or to the IP address of the interface chosen if
client_address equals 0.0.0.0. Pretend to be at the given hardware
(MAC) address. The chaddr field is set to hardware_address. Unless the
broadcast bit is also set, this usually means that no replies will be
received, as the server or relay agents will normally try a link-level
unicast to the phony address. Sets the hostname option in the outgoing
packet to the given value. Sets the client identifier option in the
outgoing packet to the given string. The string is treated literally,
not as a hex representation of an arbitrary octet string. Sets the IP
address value in the outgoing packet. This option is required if the
outgoing packet is to validly represent a client in the DHCP states
selecting or rebooting or in a DHCP DECLINE message. The string fol‐
lowing determines the kind of BOOTP or DHCP packet sent, and whether
the packet is broadcast or unicast. The default is to emulate a BOOTP
client. Sends a packet of size octets (by default 548 octets). Exits
after timeout seconds if no responses are received. Sets the file
field in the outgoing packet to the given string.
DESCRIPTION
The dhcpcemu command emulates a DHCP/BOOTP client. Options are pro‐
vided to set the most important fields in the BOOTP request packet. A
packet is constructed, is sent through the interface specified, and a
reply awaited. The emulator exits after the first reply is received or
for a length of time specified by the -t option. Depending on the
options specified and/or the DHCP server configuration, no reply may in
fact be forthcoming. If no timeout is specified, the emulator may be
killed with any suitable asynchronous signal. The SIGINT signal (usu‐
ally generated from the keyboard with Ctrl/c) is available if dhcpcemu
is running in the foreground.
It is important to note that with the options available, it is quite
possible to create an illegal packet. This is one of the primary func‐
tions of dhcpcemu; to test the behavior of servers when confronted with
packets that do not conform to the standards.
RESTRICTIONS
A cluster member should never be a DHCP client. It should always use
static addressing.
If a cluster is to support a DHCP server, there can be only one DHCP
server for all the cluster members using a common database with
failover.
SEE ALSO
RFC2031, RFC2032
dhcpcemu(8)
