Ip Helper-Address - Enterasys SecureStack C2 Configuration Manual

ip helper-address

Defaults
None.
Mode
Interface configuration: C2(su)‐>Router1(Config‐if(Vlan 1))#
Usage
Directed broadcast is an efficient mechanism for communicating with multiple hosts on a network
while only transmitting a single datagram. A directed broadcast is a packet sent to all hosts on a
specific network or subnet. The directed broadcast address includes the network or subnet fields,
with the binary bits of the host portion of the address set to one. For example, for a network with
the address 192.168.0.0, the directed broadcast address would be 192.168.255.255. For a subnet
with the address 192.168.12.0, the directed broadcast address would be 192.168.12.255.
In order to minimize broadcast DoS attacks, forwarding of directed broadcasts is disabled by
default on the SecureStack C2, as recommended by RFC 2644.
If the ability to send directed broadcasts to a network is required, you should enable directed
broadcasts only on the one interface that will be transmitting the datagrams. For example, if a
SecureStack C2 has five routed interfaces for the 10, 20, 30, 40, and 50 networks, enabling directed
broadcast only on the 30 network interface will allow anyone from any other networks (10, 20, 40,
50) to send directed broadcast to the 30 network.
Example
This example shows how to enable IP directed broadcasts on VLAN 1:
C2(su)->router(Config)#interface vlan 1
C2(su)->router(Config-if(Vlan 1))#ip directed-broadcast
ip helper-address
Use this command to enable the DHCP/BOOTP relay agent on a SecureStack C2 routed interface.
Enabling the relay agent allows forwarding of client DHCP/BOOTP requests to a DHCP/BOOTP
server that does not reside on the same broadcast domain as the client. Up to 6 IP helper addresses
may be configured per interface.
The no form of this command disables the forwarding of UDP datagrams to the specified address.
Syntax
ip helper-address address
no ip helper-address address
Parameters
address
Defaults
None.
Mode
Interface configuration: C2(su)‐>Router1(Config‐if(Vlan 1))#
16-12 IP Configuration
Address of the host where UDP broadcast packets should be forwarded.