DHCRELAY(8) FreeBSD System Manager's Manual DHCRELAY(8)
NAME
dhcrelay - Dynamic Host Configuration Protocol (DHCP) relay agent
SYNOPSIS
dhcrelay [-dor] [-C circuit-id] [-R remote-id] -i interface
destination ...
DESCRIPTION
The dhcrelay 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.
dhcrelay listens for DHCP requests on a given interface. When a query is
received, dhcrelay forwards it to the list of DHCP destinations 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 server might be a name, address or interface. dhcrelay will operate
in layer 2 mode when the specified servers are interfaces, otherwise it
will operate in layer 3 mode.
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
dhcrelay should attempt to configure, must be specified on the command
line.
dhcrelay supports relaying of DHCP traffic to configure IPsec tunnel mode
clients when listening on the enc(4) interface using layer 3 mode only.
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:
-C circuit-id
The circuit-id relay agent information sub-option value that
dhcrelay should append on relayed packets. If this option is not
specified, it will use the interface number by default.
-d Do not daemonize. If this option is specified, dhcrelay will run
in the foreground and log to stderr.
-i interface
The name of the network interface that dhcrelay should attempt to
configure. For layer 3 mode at least one IPv4 address has to be
configured on this interface.
-o Add the relay agent information option. By default, this is only
enabled for the enc(4) interface.
-R remote-id
The remote-id relay agent information sub-option value that
dhcrelay should append on relayed packets. If this option is not
specified, it will use the destination address by default.
-r Replace incoming Relay Agent Information with the one configured.
SEE ALSO
dhcpd(8), dhcpleased(8)
STANDARDS
R. Droms, Dynamic Host Configuration Protocol, RFC 2131, March 1997.
S. Alexander and R. Droms, DHCP Options and BOOTP Vendor Extensions, RFC
2132, March 1997.
M. Patrick, DHCP Relay Agent Information Option, RFC 3046, January 2001.
B. Patel, B. Aboba, S. Kelly, and V. Gupta, Dynamic Host Configuration
Protocol (DHCPv4) Configuration of IPsec Tunnel Mode, RFC 3456, January
2003.
AUTHORS
dhcrelay was written by Ted Lemon <
[email protected]>.
The current implementation was reworked by Henning Brauer
<
[email protected]>.
BUGS
Relayed DHCP traffic could actually safely be protected by IPsec but,
like dhcpd(8) and dhcpleased(8), dhcrelay will bypass IPsec for all its
traffic.
FreeBSD 14.1-RELEASE-p8 June 27, 2024 FreeBSD 14.1-RELEASE-p8