Use this command to configure the relay of certain UDP broadcast packets received on any interface. This command can be invoked multiple times, either to specify multiple server addresses for a given UDP port number or to specify multiple UDP port numbers handled by a specific server.
| Default | No helper addresses are configured. |
| Format | ip helper-address server-address [dest-udp-port | dhcp | domain | isakmp | mobile-ip | nameserver | netbios-dgm | netbios-ns | ntp | pim-auto-rp | rip | tacacs | tftp | time] |
| Mode |
|
| Parameter | Description |
|---|---|
| server-address | The IPv4 unicast or directed broadcast address to which relayed UDP broadcast packets are sent. The server address cannot be an IP address configured on any interface of the local router. |
| dest-udp-port | A destination UDP port number from 0 to 65535. |
| port-name | The destination UDP port may be optionally specified by its name. Whether a port is specified by its number or its
name has no effect on behavior. The names recognized are as follows:
|
Example: To relay DHCP packets received on any interface to two DHCP servers, 10.1.1.1 and 10.1.2.1, use the following commands:
(switch)#config (switch)(config)#ip helper-address 10.1.1.1 dhcp (switch)(config)#ip helper-address 10.1.2.1 dhcp
Example: To relay UDP packets received on any interface for all default ports to the server at 20.1.1.1, use the following commands:
(switch)#config (switch)(config)#ip helper-address 20.1.1.1
