Dynamic Host Configuration Protocol relay
utility provides a means for relaying
DHCP and BOOTP requests from a subnet to which no DHCP server is directly
connected to one or more DHCP servers on other subnets.
listens for DHCP requests on a given
interface. When a query is received, dhcrelay
forwards it to the list of DHCP servers specified on the command line. When a
reply is received, it is broadcast or unicast on the network from whence the
original request came.
The name of at least one DHCP server to which DHCP and BOOTP requests should be
relayed, as well as the name of the network interface that
should attempt to configure, must be
specified on the command line.
supports relaying of DHCP traffic to
configure IPsec tunnel mode clients when listening on the
DHCP server has to support RFC 3046 to echo back the relay agent information
to allow stateless DHCP reply to IPsec tunnel mapping.
The options are as follows:
- dhcrelay normally runs in the
foreground until it has configured an interface, and then reverts to
running in the background. This option forces
dhcrelay to always run as a foreground
- The name of the network interface that
dhcrelay should attempt to configure. At
least one IPv4 address has to be configured on this interface.
- Add the relay agent information option. By default, this is
only enabled for the
Dynamic Host Configuration Protocol,
RFC 2131, March 1997.
S. Alexander and
R. Droms, DHCP Options and BOOTP
Vendor Extensions, RFC 2132,
DHCP Relay Agent Information Option,
RFC 3046, January
B. Aboba, S. Kelly, and
V. Gupta, Dynamic Host
Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel Mode,
RFC 3456, January
was written by
The current implementation was reworked by Henning
Relayed DHCP traffic could actually safely be protected by IPsec but, like
will bypass IPsec for all its