IP Configuration Command Set
Configuring Broadcast Settings
Matrix E1 Series (1G58x-09 and 1H582-xx) Configuration Guide 12-25
Example
This example shows how to enable forwarding of Domain Naming System UDP datagrams (port
53):
About DHCP/BOOTP Relay
DHCP/BOOTP relay functionality is applied with the help of IP broadcast forwarding. A typical
situation occurs when a host requests an IP address with no DHCP server located on that segment.
A routing module can forward the DHCP request to a server located on another network if:
•IP forward-protocol is enabled for UDP as described in Section 12.2.4.2, and
•the address of the DHCP server is configured as a helper address on the receiving interface of
the routing module forwarding the request, as described in Section 12.2.4.3.
The DHCP/BOOTP relay function will detect the DHCP request and make the necessary changes
to the header, replacing the destination address with the address of the server, and the source with
its own address, and send it to the server. When the response comes from the server, the
DHCP/BOOTP relay function sends it to the host.
12.2.4.3 ip helper-address
Use this command to enable DHCP/BOOTP relay and the forwarding of local UDP broadcasts
specifying a new destination address. This command works in conjunction with the ip
forward-protocol command (Section 12.2.4.3), which defines the forward protocol and port
number. You can use this command to add more than one helper address per interface, up to a
maximum of 20 helper addresses per interface.
ip helper-address address
Syntax Description
Command Syntax of the “no” Form
The “no” form of this command disables the forwarding of UDP datagrams to the
specified address:
no ip helper-address address
Matrix>Router(config)#ip forward-protocol udp 53
address Specifies a destination broadcast of host address used when
forwarding.